Yamaha Super Jet Racing Modifications by Group K

The Different Super Jet Models - The Yamaha Super Jet has been a popular competition platform since it’s introduction in 1990. While many parts of the machine has remained, there have been a number of technical updates that would be important to owners considering competition level modifications. The following is a brief overview of those updates.

'90/'92 633 - Single 44mm carb, 77mm (633cc) 6M6 cylinder, smaller 6M6 reeds, 6500 rpm limiter.

'93 633 - Siphon type bilge that sacrifices less thrush, slightly larger diameter pump exit nozzle for
better thrust.

'94/'95 701 Single carb - 61X cases with larger reeds, 81mm 61X cylinder, narrow wrist pin bearings
with thrust washers, 7100 rpm rev limiter, changed impeller housing mounting.

‘96/’99 701 Twin Carb - 62T "raider" cases with larger reeds, beefier "62T" cylinder head casting,
dual 38mm carbs, "sharp nose" hull design change in ‘97.

To help parts managers to differentiate parts, Yamaha uses a particular part number "prefix" to identify
parts that are exclusive to a particular model. In many cases this prefix is cast on (cases, cylinders, and
heads) or printed on the part itself (like cdi boxes). The following are the common prefixes and the
machines they relate to. These prefixes will be referred to later in this document as they are often
important with respect to IJSBA rules.

6M6 61X 62T 64X
’90 - ’93 633cc models ’94 - ’99 701cc models ’96 - ’99 701cc models ‘97 - ’99 753cc models (non-stand-up)


1999 IJSBA Racing Classifications - The following is a general description of the Super Jet modifications allowed for each of the following IJSBA racing classes.

Stock - Allowed: Aftermarket impeller, ride plate, scoop grate, flame arrestor, primer kit, flush kit. Choke removal, re-jetting, and 1mm over-boring allowed. Aftermarket handlebars, throttles, and handle-pole pivot bushings.

Limited - In addition to stock class mods, aftermarket exhaust pipe, carburetors, compression increase, cdi unit, cooling system upgrades, and steering nozzle.

Super Stock - In addition to Limited mods, cylinder boring/sleeving/porting, case porting and interior machining, aftermarket ignition, pump assembly, waterbox, aluminum handle pole. Older models allowed to update to 62T cases and intake.

Free Style - The Freestyle rules permit all modifications with little or no restrictions.

Race Boat Platforms - If you are planning to construct a closed course race machine for top level IJSBA competition, we recommend that you start out with a '97 - '99 model machine. Other than cosmetics, there is no difference between '97 - '99 models. These models offer the best versatility, and net the biggest performance increases with any given set of mods.

For the economy minded recreational/racing rider, the '93 - '96 models can be built to be an exceptionally quick and reliable dual purpose machine (Limited and Superstock)...at a price that is much easier to live with. While these machines may be able to fare well in local level competition, they would strain to be the top of the heap in a national caliber event.

The engines of the '90 - '93 models have the same potential as the later models, however they employ a different pump mounting system that was a bit more difficult to seal to the hull...On heavily modified SuperJets that generate lots of horsepower, the "O" ring seal of these models could easily develop breeches that resulted in cavitation and thrust loss. As a result, we recommend that these models be avoided when building a high output Super Stock.

Recreational/Race Platforms/Freestyle - For this type of riding application, the early 633 models are just as effective as the newer models. SuperJets of the 633 displacement can be modified to be fast and responsive recreational machines. If the 633 displacement is not enough for your application, the affordable 701 big boring modification makes a huge difference in overall acceleration. For Freestyle riding, the 701 big bore Sleeper (using the stock pipe), and the 633cc Hammer-92 have been exceptionally popular because of their smooth quick and controllable delivery that is accompanied by the very best in long term reliability on 92 octane pump gas

About Radar testing - More than any other pwc's, stand-up machines are the hardest to compare based on radar testing. As with all radar testing, there are the variables of rider weight, position, not to mention air quality, etc. However with the stand-up machines, the rider’s weight, and their ability to maintain the machine perfectly straight at high speeds can also result in significant changes in radar numbers. Given this, we have gathered all our Super Jet data using intermediate level riders of about 200 lbs. In this way, we have reduced "some" of the potential error inherent with the radar testing of stand ups. Please note that lightweight riders, or pro level riders would likely be able to yield slightly better speeds than the data we present.

Modification level/case model radar speeds ‘90/’93-633cc (6M6 case) ‘94/’95-701cc (61X case) ‘96/’99-701cc (62T case)
STOCK 38.2 44.1 45.6
IJSBA "STOCK" N/a 47.0 49.1
Limited 1- (92 octane) N/a 50.6 51.5
Limited 2 – (105 octane) N/a 53.2 53.8
Sleeper -std bore (92 octane) 47.6 48.4 49.1
Hammer- std bore (92octane) 49.4 51.1 53.5
753cc Hammer (92octane) N/a 54.1 54.7
781cc Hammer (105 octane) N/a 55-56 57-58

About Tachometer Testing - On water testing with a digital tachometer is a big asset to confirming the increases of various modifications. Throughout this document, we will make reference to peak rpm numbers. All this data is gathered with a PET 2000 digital tach. The PET has a quick update time and excellent accuracy (besides being durable and somewhat waterproof). We would note that ALL these tach readings are on "glass water" only conditions. Tach data from non-glass conditions are questionably accurate.

The Levels of Modification

IJSBA "Stock" - Despite the title that infers "stock", the IJSBA rules do permit the installation of some modification parts. Using the correct parts, you can get a significant improvement in acceleration and peak speed (of 97 - 99 models). Group K has done extensive testing with mods allowed by the IJSBA rulers to come up with our "IJSBA Stock" kit. Some of these parts are bolt-ons. However a few parts do require special preparation to get the most out of a "stock" SuperJet.

Group K Sleeper (Freestyle) - The Sleeper kit (which uses a stock exhaust system) has been a very popular performance modification for freestylers because to the strong and smoothly progressive power delivery. With cylinder porting, head modification, carb boring and jetting, and a prop change, the Sleeper offers the maximum in stone reliable operation along with go usable power.

Group K "Limited 1 & 2" - Because the limited rules are geared towards the use of bolt on parts (some of which can become very expensive), there is a wide cost range for the construction of a IJSBA limited SuperJet. We have divided our Limited kits into 2 classifications. The limited 1 is a cost conscious approach to constructing a very competitive machine. The limited 2 is a "no holds barred" approach to constructing the same machine. The version 2 certainly has the potential to be slightly quicker and faster than the version 1, however the extra cost of the version 2 is accompanied by a higher cost maintenance schedule as well.

Group K 701cc Hammer (92 or 96 Octane) - Dollar for dollar, this modification is the most competitive combination of a fast recreational machine that can double as a Super Stock class race boat. It is, essentially, a Sleeper kit with a few select bolt on parts that net the biggest performance gains for the money.

Group K 753cc Hammer (96 or 105+ octane) - This big bore modification is for the very serious, and skilled, stand up rider. The reliability of this big bore makes it ideal for recreational riding as well as local level closed course racing.

Group K 781cc Super Stock (105+ octane only) - This modification is for the 100% serious racer. The power output requires the skill of a very strong and experienced rider. While still very reliable (by racing standards), this is a machine that requires monitoring and occasional fine-tuning to operate at peak. We recommend that only '97 - '99 models be used for this modification.

Design Weaknesses - Overall the Yamaha driveline is among the most reliable around, however there are some areas that the Super Jet owner needs to keep in mind when selecting modifications.

Head Gasket sealing - This is perhaps the single biggest weakness of the Super Jet platform engines. There are many aftermarket approaches to sealing the cylinder-to-head surface joint. Below is our perspective on these approaches, and the pros and cons of those approaches. Please note that where stock heads are concerned, you "must" use a gasket of some kind because balance of correct water flow is controlled by the passages in the gasket.

Stock Gasket - These .055" thick gaskets seal very well, however they do experience a significant amount of "crushing". That is, in the first few operating minutes, the stock head gasket collapses up to .015" from the initial exposure to the temperatures of normal operation. This collapsing makes for a big reduction in gasket surface pressure and head bolt torque. If the head is not re-torqued shortly after the first exposure to heat, a slight compression breech will develop. Once this breech takes place, no amount of retorqueing will re-seal it. Given this, we strongly recommend re-torquing after the first few minutes of operation with these gaskets.

The only serious down side to the stock head gasket, is that it makes for a very thick squish clearance in "limited" class formats (where cylinder decking is against the rules).

"O" Ring Sealing - Some performance shops modify the stock cylinder head (or manufacture "billet" heads) to accept large diameter "O" rings to seal between the cylinder and head. This system can offer great convenience to owners who regularly remove the head for the purpose of inspection or compression changes (in the case on changeable dome heads. The other big plus to the "O" ring setup is that it significantly reduces squish clearance without having to machine the top surface of the cylinder. This "O" system is the stock means of head sealing on most Sea Doo and Polaris engines.

It should be understood that an "O" ring can easily seal water away from the cylinder bores, however no "O" ring on earth is strong enough to seal back the pressures of compression. "O" ring setups depend on a relatively broad metal-to-metal mating surface to seal compression. The absolute flatness of these two surfaces is fundamental to maintaining a lasting long term seal. Herein lies the problem with some Super Jet "O" ring setups.

The stock Yamaha cylinders are an aluminum casting with an inserted steel sleeve. After the first 10 - 20 hours of operation, the sleeve actually drops a few thousandths of an inch down into the aluminum casting. This slight movement is easily accommodated by the stock head gasket, and no leak occurs. However when a racer, preparing a Limited class race boat installs an "O" ring head on to a cylinder with these slightly dropped sleeves, it is very difficult (if not impossible) to maintain a lasting seal on these "much less than perfect" surfaces. Since limited class rules prohibit "any" decking of the cylinder, it is not possible to attend to the imperfect sealing surface on the cylinder. Some shops do "surface the tops of these limited cylinders. However the risk that an observant tech official can catch this is high. Most inspectors know about this problem, and inspect for illegal surfacing. For these reasons, we do not recommend the use of "O" ring heads on Limited formats.

In Superstock class, cylinder decking and surfacing is permitted by the rules. However most competitive level SS racers will choose to go with a big bore between 84mm and 85.5mm. The extra diameter of these larger bores takes a significant chunk out of the sealing surfaces, which are trying to seal the compression pressure of a high output racing top end. Even if the "O" ring is moved to the outer reaches of the water jacketing, the surfaces will need to be perfectly lapped on a regular basis to maintain a lasting seal.

Metal Head Gaskets - For some period of time, copper head gaskets were a common aftermarket staple. While thin copper gaskets could seal well for a while, they lacked the ability to accommodate for significant deflections in the surfaces caused by localized high temperature. Since that time, many oem and aftermarket manufacturers have gone to stainless steel or heat treated steel gaskets.

The stock head gasket in the Waveblaster 2 is a .030" thick 3 layer heat treated steel gasket that has excellent sealing characteristics on an 84 - 85mm bore. This gasket offers the very best in reliable long term sealing on high output big bore platforms. It has the ability to accommodate small gasket surface irregularities, and it can be reused several times. Unfortunately, the large bore openings make it a poor choice for Limited platforms.

Our Limited 2 head mod is prepared to be used with a .10" single layer stainless steel head gasket. Used with a sealer, we feel this gasket offers the very best in squish clearance reduction, along with the ability to accommodate small irregularities and temperature deflections in the sealing surfaces of a high output limited format.

AIR LEAKS - The lower end of your engine should be totally air tight up to 8 psi. New engines pass this test with no problems. However engines with older deteriorated crank seals or brittle intake gaskets can allow outside air to leak into the lower end during operation. This "air leak" can make the fuel mixture lean enough, at high rpms, to cause a piston seizure. Air leaks, not engine modifications, are the number one cause of piston seizures on the Yamaha twin motors.

Cylinder Casting Fracturing - The 701cc cylinder castings can, and sometimes do, develop fractures in the area around the cylinder base bolts. There is some disagreement among engine builders about the true reasons behind (and potential solutions for) this fracturing. Originally it was believed that this fracturing was an exclusive result of the high horsepower output of modified racing engines. However this fracturing has appeared on many completely stock machines. It was then believed (by many engine builders) that the complete solution to avoid cylinder fracturing is to us a "girdle" type cylinder head. This term "girdling" refers to an aftermarket head (or bracketing plates) that allow the cylinder to be "captured" between the cylinder head and the crankcases. The theoretical intent of this "girdle" type mounting is to reduce the loads on the lower part of the cylinder casting, thus reducing the stresses that cause the fracturing. While it seems reasonable that this girdle type mounting may certainly help matters, we have seen plenty of girdle mounted cylinders develop fractures. Along that same line, we have also seen many big bore top ends, without girdle mounting, last several seasons without developing any fractures at all.

Our experience and observations incline us to believe that there are variations in the integrity of the individual castings. These variations result in some production parts that have a higher risk of fracturing than others (regardless of power output or mounting system). Unfortunately, no kind of x-ray or inspection process has yet been able to determine which cylinder castings may be at higher risk than others.

With all that said, we can make two recommendations. First, choose as new a cylinder as possible for your race machine (particularly if you are building a big bore). The second would be to use the R&D head with interchangeable domes, and girdle mounting kit, for any race gas engine modification set. While this head is intended to be used with no head gasket, we set up our Limited 2 kits to use it along with a .010" stainless steel head gasket, to improve long term sealing. Note that if this R&D head is chosen for an 85mm+ bore diameter arrangement, it must be special ordered direct from R&D.

About Bore Sizes – The 633's - While none of the 633cc platform machines are good choices for competitive level racing, the are ideally suited for high performance recreational use. The 633s performance can be significantly increased by big boring (accompanied by comprehensive cylinder porting). The 633 cylinders can easily be identified by the 6M6 code cast into them. Big boring the 6M6 cylinders is a very popular modification because no lower end machining of any kind is required.

These 6M6 cylinders have the most conservative porting layout of any pwc ever built. Merely increasing the bore diameter of a 6M6 cylinder (to 81mm/701cc) will not offer much benefit because the ports are so terribly undersized. For this reason, our 6M6 big bore modification is always accompanied by cylinder porting to increase flow, and a cylinder head modification to accommodate the larger piston domes.

The 701s - The 701cc Super Jet cylinders are designated by the 61X code cast into them. The stock 61X cylinder sleeves can be safely over-bored to 83mm/735cc utilizing Wiseco pistons. However the IJSBA Super Stock rules permit displacements up to 785cc (about 85.7mm). In order to get close to this displacement limit (and remain Super Stock legal) thicker sleeves must be fitted into the 61X cylinder casting. Our big bore kits include a special sleeve than not only allows diameters up to 86mm/790cc, but also has a wider head gasket sealing surface built on to it. This design change makes for a slightly more complex installation procedure, but it also makes for much easier head gasket sealing in high output applications.

It bears noting that the 701 WaveRaider comes with a 62T cylinder whose stock sleeves allow for over boring up to 84.5mm/762cc. In addition, this bored 62T cylinder bolts right on to the 61X cases with no lower end machining required. This 62T cylinder is often used by recreational riders that are looking for a less expensive big-bore option. Unfortunately, the IJSBA Super Stock rules permit "only" the 61X cylinder casting be used (and tech inspectors do look for 62Ts).

Piston Diameter Wiseco available OEM Available 6M6 stock cyl 61X stock cyl 61X sleeved cyl
77.0mm Yes Yes 633cc    
77.5mm Yes Yes 641cc    
78.0mm Yes Yes 649cc    
78.5mm Yes No 658cc    
79.0mm Yes No 667cc    
81.0mm Yes Yes 701cc 701cc  
81.25mm No Yes 705cc 705cc  
81.5mm Yes Yes Requires sleeving 710cc  
82.0mm Yes Yes   718cc  
83.0mm Yes No   735cc  
84.0mm Yes Yes   Requires sleeving 753cc
84.25mm No Yes     758cc
84.5mm Yes Yes     762cc
85.0mm Yes No     771cc
85.5mm Yes No     781cc
86.0mm Yes No     790cc

(All displacements shown are on a 68mm stroke)

About Cylinder Porting - All Group K Sleeper and Hammer kits include cylinder porting. In the past, cylinder porting has received an undeserved reputation as a modification that causes a loss of low end power and reliability. If cylinder porting is performed by someone with very little Yamaha experience, that may be true. The porting mods used in all of our kits are the result of many months of performance and wear evaluation testing. We confidently claim that Group K cylinder porting will yield a wider power band and longer piston life than "any" other porting modification available anywhere.

All Group K modified cylinders and heads are typically prepared as matched pairs to assure that you have the proper squish clearance and compression ratio for the quality of gasoline that you intend to use. These matched cylinder and head specifications play the key role in determining the amount of overall power that the engine can make, as well as the quality of fuel that you must use.

The 633's - As previously mentioned, the 6M6 633cc cylinders have uncommonly restrictive porting. We consider cylinder porting to be among the first and most important performance modifications for any 633-based platform. Few pwc's gain as big a share of overall power from cylinder porting as 633 Super Jets. Even with these big increases in port area, the 633 ported cylinders have excellent long-term piston and cylinder wear characteristics.

As mentioned above, this cylinder porting issue becomes even more pronounced for 633 cylinders that are big bored to 701cc. We will not big bore any 6M6 cylinder without also performing the port work to it.

The 701s - The 61X 701 cylinders, used on the '94 - '99 SuperJets, has considerably more port timing and port area than 633cc cylinders (bored or not). This additional port area makes for much better potential in the limited class where no port work is permitted. That said, the 701cc 61X cylinders also have the worst sleeve to cylinder casting mismatch of any pwc in the industry. Group K porting on these cylinders offers increased port timing and area values, as well as complete addressing of all the port passage mismatching. The net result is a big increase in power, from the bottom to the top of the rpm range.

About Case Porting - Super Stock is the only IJSBA racing class that allows crankcase porting and matching. This is a modification that can make a "noticeable" improvement in overall power. While the power increase from case porting is not considered "huge", it is a very desirable modification to many owners because it comes without any loss of reliability at all. The case porting is an "all gain - no lose" modification. Because case porting does aid in cylinder filling, it does become more beneficial as cylinder displacement gets increased. For this reason, we recommend that case porting be done on any Big Bore Hammer intended for competitive applications. (parts required: cylinder and top case half)

About Compression - While compression is not the only specification that designates what octane of fuel you can get away with using...it is among the most important. It has been popular for many shops to designate what "indicated compression" ratio (as found with a compression gauge) is ideal for any given fuel octane/engine arrangement. While indicated numbers (from a gauge) are reasonable benchmark reference point for wear or damage, they are by no means accurate enough to use as primary setup data. Indicated numbers lost large levels of accuracy as a result of variations in cylinder/piston condition, ring wear, and the varying speeds that starters can spin different displacement pistons.

For this reason, our technicians do not discuss indicated compression numbers connected with any of our kits. The compression ratios we use are a function of overall cylinder height, exhaust port height, head volume, etc. We test, in fine increments, to find which ratios yield the best in overall performance and temperature control for the octane and horsepower output of each particular setup. The margin between an acceptable ratio, and an unacceptably high ratio, takes place in finer increments that any compression gauge can accurately repeat within.

Octane Options - All of our Super Jet kits are designated with a particular "minimum" octane requirement: 92 (unleaded pump); 96 (50/50 mix of 92 and 100 avgas); and 105+ (race fuel). In short, the more power you make, the more heat you make. As the engine heat escalates, so will the octane requirement to operate reliably. There is no shortage of customers calling us who want to engineer a way to get race gas horsepower from a 92 octane pump gas set up...presumably by mixing and matching different modifications or parts. Please know that we have already run the full gambit of that process. If there was "any way" we could get more reliable power from the pump gas setups we sell…"we would do it". There is no magical combination of mods that we have overlooked in this area. This being the case, each owner needs to decide between the octane of fuel they are willing to purchase, and the power they want.

Not many folks want to drive a long distance to spend $5.00 a gallon on race fuel for their recreational pwc. However anyone that has paid an expensive bill for the repair of a seized piston has considered it. The repair cost of a seized piston is the financial basis we use to look at the cost effectiveness of various octane options. The average repair bill for a seized piston is about $350 for a twin cylinder pwc.

By far the most cost effective octane option is the "96 octane" 50/50 mix of pump gas and avgas. A gallon of 100 octane avgas costs about 50 cents more per gallon than 92 octane unleaded. Based on a 5 gallon tank of gas, the repair cost of one seized piston would be equal to the added money it would cost for 280 tanks full of 50/50 (100 octane avgas/92 pump gas).

Another 96 octane option is a 25% mix of 110 octane race gas with 92 pump. With race gas at $5 per gallon, you could buy 56 tanks of this mix to equal the repair of a seized piston.

Lots of owners ride in areas where they need to buy fuel at outlets on the water. These folks are more interested in octane "boosters" that they can carry along. Unfortunately no octane booster can turn 92 octane into 96. At best, 3oz of booster per gallon can normally make 87 into 91, or 92 into 93.5 - 94 (the increase offered by booster becomes less as base octane gets higher). Using more than 3oz per gallon offers no further increases. In addition, this small increase from octane booster comes at an expensive $1 more per gallon (the 25% mix of race gas costs $1.25 more per gallon).

Exhaust Systems - All Group K Limited and Hammer kits are intended to utilize either the "Factory Pipe" brand (on the 701cc engines) or Coffman aftermarket exhaust pipe (on the 633 & 633 Big Bore engines). We do not currently recommend any other pipes for our Super Jet engines.

Owners looking for an exceptional increase in acceleration may also wish to get the optional ECWI (electronically controlled water injection) system from Factory Pipe. It’s important to understand that while this system greatly improves power from 3500 - 6500 rpm, it makes no change in peak rpm or peak water speed abilities. We would also note that the big bore kits already make so much power in the middle rpm range that the added power increase of ECWI (on a stand up) might only serve to make the machine harder to keep hooked up, not actually faster. We recommend that Hammer kit owners evaluate the "controllability" of hook up on their modified Super Jet before choosing to install ECWI.

We recommend that a stock waterbox silencer be used on all our Super Jet kits. Contrary to common belief, the stock Yamaha waterboxes yield excellent overall power levels in all high output applications (even on the big bores). Unlike most after market waterboxes, the stock waterboxes can offer quiet sound levels along with strong power...even when water is diverted away. We have tested numerous aftermarket waterbox replacements and found none that comply with IJSBA sound level mandates, "and" significantly increased overall power.

Inlet Systems

SINGLE CARB 633's and 701's - All of the Group K engine kits for the single carb 6M6 case-633cc and 61X case-701cc platforms are developed to retain the single carb intake system. Our testing showed us that these engine kits (with a well prepared single carb intake) can often generate as much speed as most riders would ever need, along with very easy tuning and maintenance.

The 633/701 Hammer 96 and Sleeper kits can both use your existing Mikuni "Super BN" 44mm carb, with internal circuit upgrades. These upgrades allow the carb to feed fuel at the increased rates demanded by the ported cylinder.

The only single carb arrangement that we found to be a substantial improvement over the upgraded 44 Mikuni was the SBN46 Mikuni. The 46 Mikuni, and a 3" tall K&N flame arrestor, allowed the single carb Super Jet to accelerate, and top speed, with authority that easily matched many dual carb setups.

All our single carb kits (except the IJSBA stock) utilize a modified intake manifold plate. This modification offers noticeably improved throttle response and acceleration at a very reasonable price (note: this mod makes no change in peak rpms). This is an "all gain - no loose" modification that we recommend for all single carb arrangements.

Aftermarket dual carb kits are commonly used on 6M6 and 61X crankcase engines because they can offer slightly better mid range acceleration than a single carb arrangement. With plenty of time invested in tuning, some aftermarket dual carb sets can be made to operate better than a single in every way. However our testing showed many aftermarket "duals" to be questionably faster and unquestionably harder to maintain than the single carb. Based on these tests, we consider dual carb kits on 6M6 and 61X cases to be a questionably wise purchase for most recreational riders.

DUAL CARB 701cc PLATFORMS - The stock dual 38 Mikuni carbs (on '96 - '99 62T cased engines) are badly obstructed at the air intake mouths by the choke butterflies and other casting bosses. The Group K modification for these carbs not only removes these obstructions, but also slightly increases effective carburetor throat diameter. The Group K modified 38's are likely the very best in quick overall acceleration, and impeccable throttle control...at a very affordable cost.

For the more serious recreational rider, or closed course racer, we recommend the Novi XR modified Mikuni carbs. These carbs, while a bit expensive, are the very best in the business for CFM ability and signal strength. We recommend the 44mm Novis for our Limited 2 kit, and the 46mm Novis for the 105 octane Hammer Big Bore kits. While these carbs can still utilize the stock reed cage assemblies, they do require different manifolds and flame arrestors.

For owners seeking a more affordable approach to dual 44's (on 62T cases), we strongly recommend the stock arrangements found on the Blaster 2 and 760 WaveRaider. While these 44's do not have quite the CFM abilities of the Novis, they are a very effective alternative that offers great power along with easy installation and tuning.

Reeds - The aftermarket is full of replacement reed petals and cages for all three of the different Super Jet lower ends. The main considerations for alternative reed petals are performance, longevity, and side effect damage from petal failure.

Yamaha employs stainless steel reed petals in all the 6M6 and 61X cased Super Jets. Some of the 62T cased Super Jets came with stainless steel petals, and some with non- metallic "fiber" reed petals. The stainless steel material is used because it has an outstanding flexibility to weight ratio, the metal material seals exceptionally well against the rubber coated reed cages. Regardless of which material Yamaha chose, all the stock Yamaha reed petals offer excellent overall power characteristics. From a sheer performance standpoint, there are no aftermarket reed petals that out perform the stock petals by any big margin. All the stock Yamaha reed petals also offer exceptionally good long-term reliability.

Unfortunately, after enough service time, the stainless steel metal reeds can eventually fracture and break apart. When these stainless steel petals break, and circulate through the engine, they have the ability to cause serious damage to virtually all the internal engine moving parts (pistons, bearings, etc). If a fiber reed petal breaks apart, the engine easily "digests" the material resulting in no engine damage at all. While this reed petal fracturing is not a big problem on stock engines, the added pressures of high performance modification can significantly shorten a metal reed petal’s life.

For most recreational riders, the stock stainless steel reeds (replaced every 2 seasons) are likely the best overall performance value. However for any owner preparing a Limited 2, or Big Bore racing engine, we would recommend the use of non-metallic reed petals. Owners of 62T lower ends can simply purchase the stock Yamaha fiber petals used in the later models. For 6M6 and 61X case owners that wish to convert to fiber petals, we recommend the reeds from Carbon Tech. In this application, the Carbon Tech reeds appear to offer the best aftermarket mix of good performance, good longevity, and good cage sealing. Carbon Tech offers different material tensions for their reed petals. The "LT" (low tension) petal should be used in Limited packages to maximize the low end improvement. The "HT" (high tension) petals should be used in all other modified applications. These petals should be replaced annually in recreational engines, and inspected every 15 operating hours in racing engines.

About Reed Stuffers - "Reed stuffers" is an industry term that describes a plastic insert that smoothly guides the incoming mixture from the round profile of the carb throat, to the rectangular profile of the reed cage. The net result of reed stuffers is usually a small improvement in overall acceleration and response. Stuffers generally have no effect on peak rpm. The '96 - '99 62T engines are the only Super Jet engines that employs a design that can utilize reed stuffers. Reed stuffers are not required on the 6M6 and 61X engines.

Upgrading to Larger Reeds - Many 633cc owners have considered upgrading from the 61X crankcases which hold slightly larger reed cages. While these larger cages can be an advantage on a higher rpm racing package, The improvement on a recreational (pump gas) arrangement would be narrow. We have built plenty of "very fast" 701cc engines that employed the 6M6 633cc style reed cages.

Much the same situation exists for 61X case owners wishing to upgrade the larger reed 62T cases. Going to the 62T cases is only worth the cost if you intend to construct a very high-output racing package

Flame Arrestors – Single Carbs - The stock flame arrestor assembly on all the single carb engines works surprisingly well, and offers good protection from heavy water exposure. For customers who don’t ride in "big water" (that exposes the engine compartment to water) an aftermarket arrestor can be an asset. We recommend the 3" tall K&N non-fiber element with a short adapter.

Dual Carb Arrestors - For all the dual 38mm carb setups, we had the best performance results with the R&D Pro Lock flame arrestor. As well as offering good performance, this arrestor slips on and off easily to allow quick access for carb adjustments. Note that the Novi carburetors must be ordered with the "Pro Lock" adapters built on, in order for this arrestor to be used on them.

Ignition Systems - Of all the components of the Super Jets, few are as reliable as the stock ignition system. While different models have different rev limiter characteristics, they all share the same reliability and effective function. Even on our full out racing packages, we attempt to retain as many of the stock ignition components as possible. For this reason, our ignition mods for all of our kits consist only of rev limit changes made to the stock cdi box, and changes in ignition flywheel mass.

633 Engines - All the 633 (6M6) Super Jets have a stock cdi box with a 6500 rpm limiter. This stock limiter is okay for use with a Sleeper kit. However this limiter must be raised for effective use of any of the Hammer engine packages (where a higher revving aftermarket exhaust pipe is used). Pro Tec performs a modification to the circuitry of the stock cdi box that we consider to be the most effective and affordable rev limiter modification for the Super Jet. This Pro Tec modification comes with an adjustment for the limiter that allows for 7100 - infinity peak ability.

701cc Engines - All the 701cc Super Jets (61X and 62T crankcase) come standard with a rev limiter that falls between 7050 and 7150 rpm (there is a factory spec variation). Like the 633's, Pro Tec also makes the best rev limiter modification for these models of ignitions. It bears noting that this rev limiter mod is not required for recreational level 92 octane modification sets. In truth, many of the 100 octane formats can easily operate within this rev limit as well...on smooth water. The main benefit of the rev limiter mod on the Super Jets is noticed when the machine is operated in rough water only. As a boat is run across rough water at high speed, the engine can easily "bump" the limiter each time the pump comes out of the water (that’s allot). When an engine, that is against the limiter, reconnects with the water, there is a momentary "landing with the brakes on" kind of feeling that makes it difficult to maintain steady high speed control. The rev limiter modification does not actually increase speed across rough water, but rather it eliminates this landing with the "brakes on" feeling that can cause the rider great difficulty during a race.

Ignition Flywheels - All Super Jets use the same stock steel ignition flywheel. As a percentage of the total rotating mass of the crankshaft, this flywheel is relatively small. Despite that, quicker throttle response can be had by reducing the flywheel’s weight. There are many shops that lighten the stock flywheels (Group K included). We have experimented with many different lightening modification levels on these flywheels. It is possible to lighten the stock flywheel by as much as 1.5 pounds. However our testing showed that when the stock flywheel is lightened by this margin, there is a very high risk of fracturing, and eventual flywheel disintegration (a very destructive failure). The lightening modification that we found to have no long-term reliability weaknesses reduces total weight by .4 pounds. While this is not a big reduction in total weight, we remove this weight near the outer perimeter of the flywheel (where it has the greatest effect on total inertia). The end result is a very noticeable increase in throttle response and acceleration, as well as no compromise in long term flywheel life (note: IJSBA only permits this mod in freestyle and Super Stock classes).

Lightweight aluminum "charging" flywheels (to replace the stock steel unit) have become common in the aftermarket. These lightweight flywheels (legal for use in freestyle and Superstock) can offer big reductions in rotating mass, that generate big increases in engine acceleration rate. While many racers have used these flywheels successfully, they can cause a "side effect" problem in a stand up application.

Most racers interested in a super-light aluminum ignition flywheel, for a Super Jet, are Super Stock class racers. Most of these racers are running big bore top ends in the 771cc - 781cc range. These large displacement top ends generate so much sheer horsepower that they can make a stand up machine very difficult to control, and even more difficult to keep hooked up. The increased engine acceleration from an aluminum flywheel (on a stand up) further complicates these problems. We have seen many instances where riders installed the lighter flywheel, and then cut slower laps as a result of increased difficulty keeping the pump hooked up. Some of this "hook up" problem can be resolved by installing a stainless steel Skat Trak pump assembly. The rest of the hook-up difficulties are left up to the rider.

Our basic recommendation for any non-pro racer (using a stock pump case) is to lighten the stock ignition flywheel. For pro racers that will be using the Skat Trak pump, get the aluminum flywheel...and eat your Wheaties (you’ll need ‘em).

Total Loss Ignitions - It has been popular for so top level pro racers to fit an aftermarket "total loss" ignition. The term total loss means that there is no charging system at all. The battery provides all the voltage needed to make sparks...and that energy is totally lost (instead of being replaced by a charging system). The lightweight flywheels of total loss ignitions can offer a huge increase in engine acceleration (for those that can handle it).

We have experienced "random" reliability with total loss ignitions to such an extent, that we will not fit them to any of our engine packages. If you choose to use a total loss ignition unit, be sure that you have a contact person at the purchase point that can help you with technical and/or diagnostic issues.

Cooling Systems - All of our kits include cooling system modifications of one sort or another. The following is our in-house terminology for the different types of cooling systems.

"Controlled" System - This refers to a cooling system whose total volume ability is controlled to a less than maximum flow capability. Our only Super Jet kit that uses a controlled system is the IJSBA stock kit.

Bypassed System - This refers to a system that maintains the stock cold-water inlet to the engine, yet has additional water outlets on the cylinder head for added cooling. This system is employed in all our pump gas Sleeper and Hammer kits.

Split System - This refers to a splitting of the water coming in from the single water input line. The cold incoming water is split to allow separate feeds to the top-end and the pipe. The intended advantage is to provide a smaller amount of cold water to the pipe, so that a larger amount of cold water can be processed through the top end (via bypass outlets overboard). This is most popular on recreational engine arrangements using an aftermarket pipe, where the owner wants to avoid the hassles of installing a second cold water input line.

Dual Waterline System - This refers to a system that has two cold water input lines from the pump to the exhaust manifold. There are a wide array of outlet/bypass options on this system. Dual Cooling can be employed on any racing engine platform (except IJSBA stock). The greatest advantage to this layout is that there is a backup water inlet system in the case of a blockage entering an input line.

Parallel System - This refers to a dual water line input, where the top-end and exhaust system are treated as two separate and parallel systems. This layout (used primarily by racers) allows the use of numerous bypass outlets on the cylinder head without affecting water pressure into the exhaust system. This setup offers the best in tunability, however a blockage in either input line will bring the machine to a stop (whether by a burnt pipe coupler or a burnt piston). This arrangement also requires separate flush fitting for each system.

Note that our instructions do not offer recommended plumbing schematics for the Split, or Parallel systems. We consider these to be custom arrangements that require individual tuning to suit the particular machine needs.

Crankshaft - Few moving engine parts are more durable, or trouble free, than the crankshafts in the Super Jet engines. Truing and welding is a popular racing preparation for the crankshafts in many high performance pwc's and we strongly recommend it on a high-rpm racing platform. However truing and welding is questionable necessary for most Super Jet owners. Since the net boat/rider weight of the Super Jet is a fraction of the weight of a runabout, the crank experiences a lot less torsional loading. In addition to that, a stand-up is hard pressed to induce the same crankshaft "hook-up load" in comparison to most runabouts. We have constructed numerous high performance Super Jet packages with stock crankshafts...and never had a single crank failure. We only mandate truing and welding for race gas big bore setups.

Impellers - Impeller replacement is absolutely mandatory because all stock Super Jets come with an aluminum impeller that cavitates badly. We consider the Solas "I" pitch prop to be the most effective replacement for use with the stock pump case. This Solas prop offers excellent overall hookup, as well as the best peak speeds of any other impeller. When the Solas props for Super Jets were first released in 95-96, the steeper "J" pitch appeared to be best for the Super Jet. However since then, Solas has made a design change (without telling anyone) that made the full line of 144mm Yamaha impellers "act steeper". That is, this newer design loads the engine much harder (we suspect as a result of a steeper "root pitch"). The end result is that the current "off the shelf" Solas "I" prop is much too steep for most applications (and it is the mildest pitch that Solas offers). Group K re-pitches the current Solas "I" prop to suit the particular engine sets we sell. We call those pitches Spec1 and Spec2. The correct pitch is denoted on the price list for each modification level. For customers who wish to have their existing Solas "I" re-pitched, we do so for $48. If you purchase your Solas "I" from us at the regular cost, the re-pitching is included free.

Pump Options - For most high performance recreational applications, the stock Yamaha pump assembly works fine. For owners that want to "fine-tune" the stock pump, we recommend pump blueprinting. This pump blueprinting does not increase smooth water peak speeds, however it can make a noticeable improvement in rough water hook-up ability.

For more serious racers, the stainless steel Skat Trak 12 vane "C-75" pump assembly is the last word in pump mods. This (somewhat expensive) assembly offers incredibly good rough water hook-up that cannot be matched with any other pump setup. It bears noting that the Skat pump uses a smaller diameter 140mm "swirl" type impeller (stock is 144mm). This means that any other prop you have for the stock pump cannot be used with the Skat pump. Since the IJSBA rules mandate that a stock pump "housing must be retained, Skat Trak installs their stainless steel insert into your pump case, hence your pump case "core" is required for this modification.

Handling Components - There are many different ride plates, scoop grates, etc, made by various aftermarket shops for the Super Jet. Since all riders have different handling preferences, it’s impossible to name any one part as "best". However it is possible to name the parts that appear to have gained the widest acceptance as "good in the most applications". With respect to ride plates, the Pro Tec plate seems to get the nod from more racing and recreational riders than any other. Many plates allow for much better tracking in the turns, but let go suddenly with little notice. The ProTec plate offers a very predictable "sliding" in high speed turns that allows the rider to feel when the plate is getting ready to "let go". In addition, the Pro Tec plate offers very good high speed tracking (for a plate with a predictable slide characteristic).

With respect to scoop grates, the Worx grate seems to be the best combination of hook up and peak speed ability. To be sure, there are more aggressive top loader grates available. But most of those grates pay a big price in peak water speed ability that comes along with a very questionable improvement in hook-up (compared to the Worx).

One popular handling item among closed course racers is a lever controlled trim nozzle (aka "dump" nozzle). This nozzle kit helps the rider to control the porpoising of the hull under hard acceleration. Such a kit is manufactured by ProTec. While a bit expensive, this trim nozzle kit is a big asset for controlling the machine during high speed operation in rough water. It took our test riders a while to get used to the operation, but once acclimated, they all preferred it. The only down side to the nozzle set was that the siphon bilge did not work as well as with the stock nozzles. Some fiddling with the siphon tube did not resolve the problem on our test unit (a longer tube in the thrust stream may do it). Since most racers have an aftermarket bilge pump fitted, this is not considered a big problem compared to the handling benefit.

Complete Engines - While many owners prefer to do their own mechanical work, there are plenty of folks that don’t consider engine assembly as "fun". For those customers, Group K can construct a complete ready to install short-block, modified to your specifications. The 150 lbs. UPS weight limit easily accommodates the Super Jet engine (about 115 lbs.) for customer outside of the Southwestern USA region.. All short blocks are assembled with all new gaskets and seals, and then pressure tested to assure no "rouge" air leaks.

Note that complete short blocks carry a $35.00 fee to cover handling and container costs.

Complete Boats - Group K can construct a complete turn key race boat to your specifications. After assembly, all complete race boats are broken in and water tested to confirm tuning and performance. Specific quotes to your specification are available for $50 billed to your Visa/MasterCard. This quote charge is applied to the cost of the machine upon ordering.

Group K "IJSBA Stock" Kit (‘96-’99 only)

Dual Carb R&D Pro-Lock Arrestor w/adapters----------------------------------------------------------194.00

Primer Kit (for choke removal)------------------------------------------------------------------------------29.00

"Spec" Flush Kit-----------------------------------------------------------------------------------------------15.00

Optional 1mm Over-boring-----------------------------------------------------------------------------------89.00

Solas "I" with Type 1 re-pitch------------------------------------------------------------------------------259.00

Solas "I" Type 1 re-pitch-------------------------------------------------------------------------------------48.00

Worx Scoop Grate--------------------------------------------------------------------------------------------150.00

Group K Sleeper (92 octane, stock exhaust)

‘90/’93-Sleeper Kit (cylinder porting, head mod, cooling upgrade,
primer kit, inlet manif mod, & carb re-jetting)------------------------------------------------------------529.00

‘96/’99-Sleeper Kit (cylinder porting, head mod, cooling upgrade,
primer kit, carb boring & re-jetting)-----------------------------------------------------------------------689.00

BIG BORE Upgrade (to 701cc for 633s   to 753cc for 701s)

Includes cylinder boring, piston assys, bigger bore head gasket set.  ---------------------- 440.00

K&N Single Carb Flame Arrestor with adapter (44 or 46)-----------------------------------------------75.00

Optional 46mm Mikuni Carb (6M6 and 61X case models)---------------------------------------------259.00

Optional Dual Carb R&D Pro-Lock Arrestor w/ adapters (62T case models)-----------------------224.00

Optional Carbon Tech "HT" Reed Petals (all models)----------------------------------------------------99.00

Optional Ignition Flywheel Lightening-----------------------------------------------------------------------75.00

Optional Pump Blueprinting (of the stock pump vain body and impeller housing)------------------210.00

Optional Bilge pump Kit with handlebar control

Solas "I" with Type 1 repitch-------------------------------------------------------------------------------259.00

Worx Scoop Grate--------------------------------------------------------------------------------------------150.00

Group K "Limited" 1

Cylinder head modification (92 octane)-------------------------------------------------------------------89.00

Optional R&D Cylinder Head with Girdle Kit & Changeable domes----------------------------------479.00

Dual Waterline Upgrade-------------------------------------------------------------------------------------65.00

Single Carb inlet manifold mod (6M6 and 61X case models)------------------------------------------55.00

Re-jetting of stock 44mm Mikuni (6M6 and 61X case models)-----------------------------------------45.00

Optional 46mm Mikuni Carb (6M6 and 61X case models)---------------------------------------------259.00

Single Carb Flame Arrestor (44 or 46) (6M6 and 61X case models)----------------------------------75.00

Dual 38 Carb Boring & Re-Jetting (62T case models)-------------------------------------------------260.00

Dual 38 Reed Stuffers (62T case models)----------------------------------------------------------------75.00

Dual Carb R&D Pro-Lock Arrestor w/ adapters (62T case models)---------------------------------194.00

Optional Carbon Tech "LT" Reed Petals (all models)----------------------------------------------------99.00

Pro-Tec CDI Rev Limiter Mod-----------------------------------------------------------------------------170.00


Factory Pipe Products Exhaust Pipe w/ Manifold------------------------------------------------------780.00

Optional Bilge pump Kit with handlebar control

Solas "I" with Type 1 re-pitch-----------------------------------------------------------------------------259.00

Solas "I" Type 1 re-pitch------------------------------------------------------------------------------------48.00

Pro Tec Ride Plate-------------------------------------------------------------------------------------------82.00*

Worx Scoop Grate-------------------------------------------------------------------------------------------150.00

Pro Tec Trim Nozzle----------------------------------------------------------------------------------------499.00*

Group K "Limited" 2

Cylinder head modification (105 octane)-----------------------------------------------------------------89.00

Optional R&D Cylinder Head with Girdle Kit & Changeable domes---------------------------449.00

1mm Over-boring--------------------------------------------------------------------------------------------89.00

82mm Wiseco Pro-Lite Pistons (each)-----------------------------------------------------------------129.00

Dual Waterline Upgrade------------------------------------------------------------------------------------65.00

Novi Max Flow dual 46mm Carb kit (carbs, & linkage)------------------------------------------------990.00

R&D Reed Stuffers (62T case models)-------------------------------------------------------------------75.00

Dual Carb R&D Pro-Lock Arrestor (62T case models)-----------------------------------------------189.00


Optional Carbon Tech "LT" Reed Petals (all models)---------------------------------------------------84.00

Factory Pipe Products Exhaust Pipe w/ Manifold-----------------------------------------------------780.00

Optional Bilge pump Kit with handlebar control

Pro Tec CDI Rev Limiter Mod----------------------------------------------------------------------------170.00

Solas "I" with Type 1 re-pitch-----------------------------------------------------------------------------259.00

Solas "I" Type 1 re-pitch------------------------------------------------------------------------------------48.00

Worx Scoop Grate-------------------------------------------------------------------------------------------150.00

Pro Tec Trim Nozzle----------------------------------------------------------------------------------------499.00

Group K 701cc Hammer

Cylinder head modification (92 or 105+ octane)--------------------------------------------------------89.00

Cylinder Porting (specify 92 or 105+ octane)----------------------------------------------------------350.00

Single Carb inlet manifold mod (6M6 and 61X case models)------------------------------------------55.00

Re-jetting of stock 44mm Mikuni (6M6 and 61X case models)----------------------------------------45.00

Optional 46mm Mikuni Carb (6M6 and 61X case models)--------------------------------------------259.00

Single Carb Flame Arrestor (44 or 46) (6M6 and 61X case models)---------------------------------75.00

Dual 38 Carb Boring & ReJetting (62T case models)-------------------------------------------------260.00

Dual 38 Reed Stuffers (62T case models)---------------------------------------------------------------75.00

Dual Carb R&D Pro-Lock Arrestor w/adapters (62T case models)--------------------------------194.00


Optional Carbon Tech "HT" Reed Petals (all models)--------------------------------------------------99.00

Optional Ignition Flywheel lightening---------------------------------------------------------------------75.00

Factory Pipe Products Exhaust Pipe w/Manifold----------------------------------------------------780.00

Pro Tec CDI Rev Limiter Mod---------------------------------------------------------------------------170.00

Optional Pump Blueprinting (of the stock pump vain body and impeller housing)---------------210.00

Solas "I" with Type 1 re-pitch----------------------------------------------------------------------------259.00

Solas "I" Type 1 re-pitch----------------------------------------------------------------------------------48.00

Worx Scoop Grate-----------------------------------------------------------------------------------------150.00

Group K 753cc Hammer Kit

753cc Big Bore Mod (84mm)(Specify 92, 96, or 105+ octane) Includes sleeves & installation, Wiseco Pro Lite pistons & boring, cylinder porting, cylinder head modification, crankcase boring (top case only), and all top end gaskets -------------------------------------------------------------------------------------------------------------1280.00

Optional R&D Cylinder Head with Girdle Kit & Changeable domes--------------------------------449.00

Optional Crankcase porting and matching-------------------------------------------------------------210.00

Dual Waterline Upgrade-----------------------------------------------------------------------------------65.00

Single Carb inlet manifold mod (6M6 and 61X case models)----------------------------------------55.00

Re-jetting of stock 44mm Mikuni (6M6 and 61X case models)--------------------------------------45.00

Optional 46mm Mikuni Carb (6M6 and 61X models)-------------------------------------------------259.00

Single Carb Flame Arrestor (44 or 46) (6M6 and 61X case models)-------------------------------75.00

Dual 38 Carb Boring & Re-Jetting (62T case models)----------------------------------------------260.00

Dual 38 Reed Stuffers (62T case models)-------------------------------------------------------------75.00

Dual Carb R&D Pro-Lock Arrestor w/adapters (62T case models)-------------------------------194.00


Optional Carbon Tech "HT" Reed Petals (all models)-------------------------------------------------99.00

ProTec CDI Rev Limiter Mod---------------------------------------------------------------------------170.00

Optional Ignition Flywheel lightening--------------------------------------------------------------------75.00

Factory Pipe Products Exhaust Pipe w/Manifold----------------------------------------------------780.00

Optional Pump Blueprinting (of the stock pump vain body and impeller housing)--------------210.00

Solas "I" with Type 2 re-pitch--------------------------------------------------------------------------259.00

Solas "I" Type 2 re-pitch---------------------------------------------------------------------------------48.00

Pro Tec Ride Plate----------------------------------------------------------------------------------------82.00

Worx Scoop Grate----------------------------------------------------------------------------------------150.00

Pro-Tec Trim Nozzle------------------------------------------------------------------------------------499.00

Group K 781cc Super Stock Hammer Kit

781cc Big Bore Mod (85.5mm - Specify 96 or 105+ octane) Includes sleeves & installation, Wiseco Pro Lite pistons & boring, cylinder porting, Cylinder head modification, crankcase boring (top case only), and all top end gaskets ----------------------------1280.00

Optional Crankcase porting and matching-----------------------------------------------------------210.00

Crankshaft Truing and Welding------------------------------------------------------------------------180.00

Dual Waterline Upgrade----------------------------------------------------------------------------------65.00

Novi Max Flow dual 46mm Carb kit (carbs, & linkage)----------------------------------------------1290.00

R&D Reed Stuffers----------------------------------------------------------------------------------------75.00

Dual Carb R&D Pro-Lock Arrestor--------------------------------------------------------------------149.00


Optional Carbon Tech "HT" Reed Petals (all models)------------------------------------------------99.00

Optional Ignition Flywheel lightening-------------------------------------------------------------------75.00

Factory Pipe Products Exhaust Pipe w/ Manifold---------------------------------------------------780.00

Pro Tec CDI Rev Limiter Mod-------------------------------------------------------------------------170.00

Optional Bilge pump Kit with handlebar control

Billet Aluminum Drive Couplers------------------------------------------------------------------------150.00

Pump Blueprinting (of the stock pump vain body and impeller housing)------------------------210.00

Solas "I" with Type 2 repitch---------------------------------------------------------------------------259.00

Solas "I" Type 2 re-pitch---------------------------------------------------------------------------------48.00

Optional Skat Trak Stainless Steel "C-75" Pump (exchange) w/ Swirl Impeller---------------1340.00

140mm Swirl Impeller (for Skat Trak pump)---------------------------------------------------------259.00

Worx Scoop Grate---------------------------------------------------------------------------------------150.00

Pro Tec Trim Nozzle------------------------------------------------------------------------------------499.00

Misc. Labor

Complete engine Tear Down, reassembly, and pressure test------------------------------------350.00

Cylinder boring, chamfering, and finish honing (one oversize, 2 holes)-------------------------90.00

Case Machining (to accommodate big bore sleeves)-----------------------------------------------60.00



GETTING THE WORK DONE - Most customers send GROUP K the parts needed for modification via UPS, and then do the engine assembly work themselves. We also do complete engine and pump assemblies for customers who want a finished unit ready for installation. The new 150 lbs. UPS weight limit makes engine shipping practical and affordable.

All orders prepaid with a cashiers check or money order will be returned freight free via ups ground service anywhere in the continental United States. All other orders will be billed to a visa/master card or sent freight collect cod cashiers check (ups no long accepts cash for cods). If you would like to pay additional for 3 day, 2 day, or 1 day return shipment, please specify your preference in a cover letter with your parts. Be sure to include your return address and day phone information in case we have any questions regarding your order.

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