62t big power options?
- Thread starter MADMAT
- Start date
accbr
addicted
- Location
- Lexington, KY
I was just reading your Envy build thread. 
oke:
I like my LPW big bore, but you already knew about those.
oke:I like my LPW big bore, but you already knew about those.
DAG
Yes, my balls tickled from that landing
- Location
- Charlotte, NC
I aposlutly love my 84mm stock bore LPW 62t.
I got to ride Pats boat with TL, Group K porting on a BB 61x, pumping C-12/220psi. and i'd be damed if mine did not hit harder. on pumpgas/180psi, enhancer, and pauls port. everythign else was the same.
i highly pleased with pauls work.
I got to ride Pats boat with TL, Group K porting on a BB 61x, pumping C-12/220psi. and i'd be damed if mine did not hit harder. on pumpgas/180psi, enhancer, and pauls port. everythign else was the same.
i highly pleased with pauls work.
I've never ridden a Group K boat that really impressed me, I think they're too focused on reliability and stay conservative. However, 850cc's would make up for that probably.
A stock stroke Lamey with moderate porting would be super reliable and make awesome power like freestylegeek used to have. His old engine is or was for sale here recently.
The Jetworks 4mm stroker setup is good too and should have better torque than a non-stroked engine of similar displacement.
A stock stroke Lamey with moderate porting would be super reliable and make awesome power like freestylegeek used to have. His old engine is or was for sale here recently.
The Jetworks 4mm stroker setup is good too and should have better torque than a non-stroked engine of similar displacement.
DR3
Xscream Braaaap
- Location
- palm harbor, Fl
team scream has their big bore sleeved 771 which has epoxied cases and porting and then if you add their 5 mil to the big bore and a little more porting you get their 828 which is what pancake pete runs. i think they are also working on another setup with small pistons and a stroker crank thats suppost to rip.. give them a call theyll let ya know what they have to offer :beerchug:
accbr
addicted
- Location
- Lexington, KY
I'll be at Wavedaze in VA beach if anybody wants to try my SJ.
Mark44
Katie's Boss
- Location
- 100% one place
BruceSki
Formerly Motoman25
- Location
- Long Island
how come? j/w
i want to try the group-k 849cc
Because over time the epoxy breaks down and on heavily ported cases will cause leaks in the flywheel area. Then they need blasted and re epoxied. NO THANKS!!!! Been there done that.
BruceSki
Formerly Motoman25
- Location
- Long Island
thanks for the schooling.....
Me too! I have been talking with Harry via email.
Here is a little bit:
Yamaha 845cc Big Bore “Hammer” Modifications
The Short Version
The 845cc Kit and Performance
The Group K Super Jet 845cc Big bore kit is the most brutally powerful 91 octane engine package available for the Yamaha SuperJet engine platform. It is built to be simple, reliable, and offer instant acceleration that is unmatched by any other SuperJet engine Mod….. It is the ultimate Free-style engine package.
The 845cc Kit includes the following:
Cylinder machining, re-sleeving, and boring
Full Cylinder Porting (Freestyle Specification)
Crankcase boring (to accommodate larger cylinder sleeves)
2 – 88.5mm Group K Pistons (piston, pin, rings, & clips) (89.0mm also available)
Top end gasket set
3Bond 1211 sealer
The Specific Parts Needed for the 845cc Upgrade
Cylinder – This modification requires the use of a 62T (701 Raider) or 64X (760) cylinder core. The stock 61X cylinder is a thinner wall casting that cannot accommodate the 845cc sleeves.
Head – An unmodified stock OEM 62T (1996 or later SJ) cylinder head core must be used. We cannot use 61X (701) or 760 head cores. “O” ring heads cannot seal on this bore diameter, and cannot be used.
FPP Exhaust Manifold & Head-Pipe - The exhaust port location of the 62t/64X cylinders is very different from the stock 701cc 61X casting. The 845 requires the use of an FPP “760” exhaust manifold, or modification of your 61x FPP manifold. For an additional charge, Group K can modify your FPP 701 manifold to properly fit the 760 bolt pattern and exhaust port locations. We must have an exhaust manifold & bolts to install for final bore sizing of the 845 cylinder.
We need your FPP head-pipe & manifold to enlarge the inside bore diameters to 48mm. Doing this mod requires special fixtures, and we strongly advise against attempting this mod yourself.
Top Crankcase – The top crankcase must be machined to accommodate the larger diameter sleeves of the 845 Kit. No other lower end mods are required.
Mandatory Accessory Modifications
FPP Pipe with the “Limited” chamber Body (not the mod chamber)
FPP manifold & head-pipe inside diameter increase
Modified dual 38mm carbs, or stock oem 760 44mm carb-set
Re-Pitched Solas 13/17 Concord Impeller
A little more super delicious brain food:
The Detailed Version
Overview
In 2008, the IJSBA permitted the big boring of two-stroke Super-stock racing-class stand-up machines to 850cc. In addition, in 2007 the IJSBA has allowed the use “any modification level” of “any homologated pwc engine” in a Freestyle machine. Since that 2007 freestyle ruling there has been a flurry of huge displacement custom engines being built for pro freestyle. While their power potential is great, so is their $5000- $8000 price tags.
Back in the “real-world”, a growing number of free-style competitors, and recreational-riders are looking for a reliable and pump gas safe setup that can make pro level free-style grunt, without the pro-level maintenance or astronomical price tag.
The Group K 845cc Freestyle Big Bore was developed specifically for these freestyle enthusiasts. When developing this package, we considered it very important to specifically define the engine packages goals. Of course sheer horsepower is an important goal … but not “the” most important. The most important priority for a good freestyle setup is to have the quickest possible engine acceleration (aka response), along with a power delivery that is as linear as possible. Coupled with this engine package, needs to be a pump that can completely hook up all the power being made … especially during quick engine accelerations. While all of this sounds like the same kind of common thinking used to develop closed-course machines, there are a lot of tuning variables to accomplishing freestyle goals, that “are not” part of the average superstock closed course setup.
Besides the lower cost factor compared to the high-dollar “big block motors”, the Group K 845 offers some other important technical advantages that makes it as practical as it is effective.
Here are a few.
Crankshaft
The stock SuperJet crankshaft has a stroke that is 6mm shorter than an SXR, and 10mm shorter than the GP800 motor (being used for many big-block freestyle customs). This shorter SJ stroke means the SJ crank is considerably smaller in diameter, and whole lot lighter than an SXR or GP800 crank. This reduced rotating mass of the Super Jet engine allows it to accelerate to peak rpms much quicker than the other longer stroke motors can. In addition, the SuperJet ignition rotor is also much lighter than the others, further benefiting quick acceleration.
An added benefit of a big-bore shorter-stroke engine (like our 845), is that it experiences significantly less vibration than the other “big-bore long-stroke” motors. In every other motoring genre, large displacement long stroke twins are equipped with counter-balancers to abate the (otherwise violent) vibration that they generate (as is the case on the Sea Doo 951s). The current crop of custom big-block free-style motors have no counter-balancers …. And consequently deliver violent vibration at a wide range of engine speeds. The dramatically milder vibration of the 845 improves the long term reliability of every part of the hull and drive train.
Perhaps the greatest advantage of this lesser vibration is that the carburetors are able to calibrate much more precisely. Among many other carburetion issues, excessive vibration can easily shake the float needles away from the seats. This causes an on going rich condition at low throttle openings that is virtually impossible to “tune away”. The reduced vibrations of the 845 allow consistent needle to seat contact that results in much easier low speed fine tuning. This easier low speed tuning allows for very precise low range carburetion. Precise low-speed carb calibration is a fundamentally important component of getting the instant throttle response that a pro freestyle setup must have.
Why not a Stroker Crank
To be sure, the displacement of a longer stroke is always nice, but in the case of this particular engine setup, crank stroking brings some very negative technical luggage (besides added vibration). Because of the changed stroke geometry, when you increase the stroke of any engine, the port timings become inherently increased (longer in duration). Any stroke increase worth doing on the SJ crank (4-6mm) would result in port timings that are much more radical than what you would want for a pro free-style motor. In addition to that, most stroker motors need a spacer plate under the cylinder to keep the pistons from poking out of the top of the cylinder. Installing this spacer plate (as most strokers have) would increase port timing even more, and result in port timings that are close to the upper limit for a high rpm closed course setup … and far more than what you would want or need for a good free-style powerband.
The last handicap of the stroker crank is “rod angle”. When you increase the stroke of any crank, you also increase the rod angle when the crank is between top dead center and bottom dead center. This means that, on the power stroke, the piston is pushing down on a rod that is at a much steeper angle. This steeper rod angle results in increased piston-face/cylinder-wall wear, as well as much more stress on the rod bearing surfaces. Normally, these combined problems are resolved by installing a longer connecting rod. Sadly, by the time you add the cost of crank stroking, longer custom rods, and the thick cylinder spacer plate to accommodate that rod length, the resulting package cost increase would be about $2000+. The saddest part of such a setup is that, once built, it would always require a cylinder and head with “long-rod stroker” specs that cannot work on a stock stroke lower end. In contrast, the Group K 845 crankcase can easily accept any conventional 760 or 701 top-end in future applications.
About the 845 Modification _ Cylinder
For many years, Group K has be building 85-86mm re-sleeved big bore kits for the 61x cylinders that come stock on all ’95 and later SuperJets. Unfortunately, the 61X cylinder casting doesn’t have enough “beef” or excess material to safely accommodate the 845cc sleeves. Fortunately, the stock 62T 701 & 64X 760 cylinder casting both have quite a bit more “beef” than the old 61X casting, and they do allow for the fitment of the 845cc sleeves.
With respect to cylinder head castings, the earlier 61X head casting does not have enough wall thickness to allow for reliable sealing on the 89mm diameter, and 760 heads have a stock dome design that does not lend it well to the 845 modification. However the stock “64U” 1996+ SJ head casting has a dome design that is ideal for modification to 89mm, and it also has the casting ”beef” to maintain a lasting seal.
What this means is, anyone wanting the 845cc big bore must get a 62T or 64X cylinder, and a 1996+ 701 “62T” head for the project. For customers who do not want to hassle the process of finding these parts, Group K will have good condition used core cylinders & heads available.
Exhaust Manifold & Head-pipe
Even though the 701 & 760 cylinders have the same exhaust manifold bolt pattern, the “exhaust port location” within that bolt pattern is different between the 701 & 760 castings. This means that anyone who has the popular FPP “B” pipe on their 701, will have to either purchase a new FPP 760 exhaust manifold to match the different 760 exhaust port location, or have Group K modify their 701 exhaust manifold to match the port window sizes and locations of the new cylinder. An added detail is the big variation in port diameters on the FPP manifolds and head-pipe. The early FPP SuperJet pipes had an exhaust manifold/head-pipe inside diameter of 43mm. While this diameter offered enough exhaust port area for most 701s, it seriously choked big-bore versions of the SJ engine. In later years, FPP increased this diameter to 46-47mm. For our 845 kit, we increase the diameter to 48mm. This means that for each 845 kit, we must also have your FPP head-pipe for diameter increase modification.
Porting Considerations
One drawback of any big boring modification is the slight reduction in transfer port volume that takes place when fitting a larger sleeve. This is a particularly important issue for the 845 because, of course, the same transfer port passages are being asked to fill a larger displacement cylinder. While developing the 845 kit, a big concern was making every effort to maintain the maximum amount of transfer port area to insure that the new larger bores get an ample supply of fuel mixture. To help accomplish this, we kept sleeve thickness for the 845 is kept to a minimum, so that only a small amount of material would need to be bored from the cylinder casting to fit the new sleeves. In addition, transfer port opening durations were increased slightly to further assist with good cylinder filling. Finally, a boost port hole was added to the rear of the piston to increase the amount of mixture being delivered by the rear transfer port. This boost port hole also has an important second purpose. With each inlet stroke, this boost port hole (located as close as possible to the crown of the piston) allows cool inlet gases to pass across the underneath of the crown of the piston, helping to significantly reduce piston crown temperatures of the big 89mm piston crown.
Head Sealing
While “O” ring heads are a very popular technical fashion for many closed course racing platforms, sealing the large 89mm bore diameters (like the 845) is a tall order for any head, much less an “O” ring head. We built the 845 kit to utilize an all metal head gasket in order to offer the widest possible sealing surface area around the bores. In addition, the sleeves of the 845 are manufactured with a very wide sealing rim on the top flange to further increase sealing area width. This arrangement allows the 845 to have a firm and lasting head seal that cannot be matched by any “O” ring type head setup.
Carburetion
Since the 845 has such huge bores, it also has more “inlet signal” strength than any other SuperJet engine package ever built. In layman’s terms, inlet signal strength is the actual vacuum that the crankcase uses to draw fuel through the jetting circuits of the carbs. This vacuum is generated by the movement of the pistons Having a lot of “signal” is a big advantage, because stronger signal results in less temperamental carburetion, and less fine tuning for changes in altitude and weather conditions. The strong signal of the 845 kit allows very precise jetting of nearly any carb you install on it, and it will very little fine tuning for changes in weather conditions.
The stock SuperJet comes with dual 38mm SBN Mikuni carbs. Group K routinely modifies the throats and jetting of these carbs to increase air and fuel delivery for modified engines. These modified throat 38s are a very popular alternative for 701/760 SJ owners wanting to get the best of both performance and fuel range, and they also work very well on the 845 kit.
During our testing, we also used the larger 44mm carbs (and manifold) that comes as original equipment on the 760 Yamaha engines. While these carbs are a bit too large for the 760cc application, they worked perfectly on our 845 prototype. Since there is such a big focus on getting enough fuel and air to the 845, these oem 760 44 carbs are a very practical and effective choice for owners that want to get the most from their 845 kit. Unfortunately, the 44s do have considerably higher fuel consumption than the modified throat 38s. Given that, owners who have a high priority for fuel range should defiantly fit their 845 with the modified 38s.
The Detailed Version
Overview
In 2008, the IJSBA permitted the big boring of two-stroke Super-stock racing-class stand-up machines to 850cc. In addition, in 2007 the IJSBA has allowed the use “any modification level” of “any homologated pwc engine” in a Freestyle machine. Since that 2007 freestyle ruling there has been a flurry of huge displacement custom engines being built for pro freestyle. While their power potential is great, so is their $5000- $8000 price tags.
Back in the “real-world”, a growing number of free-style competitors, and recreational-riders are looking for a reliable and pump gas safe setup that can make pro level free-style grunt, without the pro-level maintenance or astronomical price tag.
The Group K 845cc Freestyle Big Bore was developed specifically for these freestyle enthusiasts. When developing this package, we considered it very important to specifically define the engine packages goals. Of course sheer horsepower is an important goal … but not “the” most important. The most important priority for a good freestyle setup is to have the quickest possible engine acceleration (aka response), along with a power delivery that is as linear as possible. Coupled with this engine package, needs to be a pump that can completely hook up all the power being made … especially during quick engine accelerations. While all of this sounds like the same kind of common thinking used to develop closed-course machines, there are a lot of tuning variables to accomplishing freestyle goals, that “are not” part of the average superstock closed course setup.
Besides the lower cost factor compared to the high-dollar “big block motors”, the Group K 845 offers some other important technical advantages that makes it as practical as it is effective.
Here are a few.
Crankshaft
The stock SuperJet crankshaft has a stroke that is 6mm shorter than an SXR, and 10mm shorter than the GP800 motor (being used for many big-block freestyle customs). This shorter SJ stroke means the SJ crank is considerably smaller in diameter, and whole lot lighter than an SXR or GP800 crank. This reduced rotating mass of the Super Jet engine allows it to accelerate to peak rpms much quicker than the other longer stroke motors can. In addition, the SuperJet ignition rotor is also much lighter than the others, further benefiting quick acceleration.
An added benefit of a big-bore shorter-stroke engine (like our 845), is that it experiences significantly less vibration than the other “big-bore long-stroke” motors. In every other motoring genre, large displacement long stroke twins are equipped with counter-balancers to abate the (otherwise violent) vibration that they generate (as is the case on the Sea Doo 951s). The current crop of custom big-block free-style motors have no counter-balancers …. And consequently deliver violent vibration at a wide range of engine speeds. The dramatically milder vibration of the 845 improves the long term reliability of every part of the hull and drive train.
Perhaps the greatest advantage of this lesser vibration is that the carburetors are able to calibrate much more precisely. Among many other carburetion issues, excessive vibration can easily shake the float needles away from the seats. This causes an on going rich condition at low throttle openings that is virtually impossible to “tune away”. The reduced vibrations of the 845 allow consistent needle to seat contact that results in much easier low speed fine tuning. This easier low speed tuning allows for very precise low range carburetion. Precise low-speed carb calibration is a fundamentally important component of getting the instant throttle response that a pro freestyle setup must have.
Why not a Stroker Crank
To be sure, the displacement of a longer stroke is always nice, but in the case of this particular engine setup, crank stroking brings some very negative technical luggage (besides added vibration). Because of the changed stroke geometry, when you increase the stroke of any engine, the port timings become inherently increased (longer in duration). Any stroke increase worth doing on the SJ crank (4-6mm) would result in port timings that are much more radical than what you would want for a pro free-style motor. In addition to that, most stroker motors need a spacer plate under the cylinder to keep the pistons from poking out of the top of the cylinder. Installing this spacer plate (as most strokers have) would increase port timing even more, and result in port timings that are close to the upper limit for a high rpm closed course setup … and far more than what you would want or need for a good free-style powerband.
The last handicap of the stroker crank is “rod angle”. When you increase the stroke of any crank, you also increase the rod angle when the crank is between top dead center and bottom dead center. This means that, on the power stroke, the piston is pushing down on a rod that is at a much steeper angle. This steeper rod angle results in increased piston-face/cylinder-wall wear, as well as much more stress on the rod bearing surfaces. Normally, these combined problems are resolved by installing a longer connecting rod. Sadly, by the time you add the cost of crank stroking, longer custom rods, and the thick cylinder spacer plate to accommodate that rod length, the resulting package cost increase would be about $2000+. The saddest part of such a setup is that, once built, it would always require a cylinder and head with “long-rod stroker” specs that cannot work on a stock stroke lower end. In contrast, the Group K 845 crankcase can easily accept any conventional 760 or 701 top-end in future applications.
About the 845 Modification _ Cylinder
For many years, Group K has be building 85-86mm re-sleeved big bore kits for the 61x cylinders that come stock on all ’95 and later SuperJets. Unfortunately, the 61X cylinder casting doesn’t have enough “beef” or excess material to safely accommodate the 845cc sleeves. Fortunately, the stock 62T 701 & 64X 760 cylinder casting both have quite a bit more “beef” than the old 61X casting, and they do allow for the fitment of the 845cc sleeves.
With respect to cylinder head castings, the earlier 61X head casting does not have enough wall thickness to allow for reliable sealing on the 89mm diameter, and 760 heads have a stock dome design that does not lend it well to the 845 modification. However the stock “64U” 1996+ SJ head casting has a dome design that is ideal for modification to 89mm, and it also has the casting ”beef” to maintain a lasting seal.
What this means is, anyone wanting the 845cc big bore must get a 62T or 64X cylinder, and a 1996+ 701 “62T” head for the project. For customers who do not want to hassle the process of finding these parts, Group K will have good condition used core cylinders & heads available.
Exhaust Manifold & Head-pipe
Even though the 701 & 760 cylinders have the same exhaust manifold bolt pattern, the “exhaust port location” within that bolt pattern is different between the 701 & 760 castings. This means that anyone who has the popular FPP “B” pipe on their 701, will have to either purchase a new FPP 760 exhaust manifold to match the different 760 exhaust port location, or have Group K modify their 701 exhaust manifold to match the port window sizes and locations of the new cylinder. An added detail is the big variation in port diameters on the FPP manifolds and head-pipe. The early FPP SuperJet pipes had an exhaust manifold/head-pipe inside diameter of 43mm. While this diameter offered enough exhaust port area for most 701s, it seriously choked big-bore versions of the SJ engine. In later years, FPP increased this diameter to 46-47mm. For our 845 kit, we increase the diameter to 48mm. This means that for each 845 kit, we must also have your FPP head-pipe for diameter increase modification.
Porting Considerations
One drawback of any big boring modification is the slight reduction in transfer port volume that takes place when fitting a larger sleeve. This is a particularly important issue for the 845 because, of course, the same transfer port passages are being asked to fill a larger displacement cylinder. While developing the 845 kit, a big concern was making every effort to maintain the maximum amount of transfer port area to insure that the new larger bores get an ample supply of fuel mixture. To help accomplish this, we kept sleeve thickness for the 845 is kept to a minimum, so that only a small amount of material would need to be bored from the cylinder casting to fit the new sleeves. In addition, transfer port opening durations were increased slightly to further assist with good cylinder filling. Finally, a boost port hole was added to the rear of the piston to increase the amount of mixture being delivered by the rear transfer port. This boost port hole also has an important second purpose. With each inlet stroke, this boost port hole (located as close as possible to the crown of the piston) allows cool inlet gases to pass across the underneath of the crown of the piston, helping to significantly reduce piston crown temperatures of the big 89mm piston crown.
Head Sealing
While “O” ring heads are a very popular technical fashion for many closed course racing platforms, sealing the large 89mm bore diameters (like the 845) is a tall order for any head, much less an “O” ring head. We built the 845 kit to utilize an all metal head gasket in order to offer the widest possible sealing surface area around the bores. In addition, the sleeves of the 845 are manufactured with a very wide sealing rim on the top flange to further increase sealing area width. This arrangement allows the 845 to have a firm and lasting head seal that cannot be matched by any “O” ring type head setup.
Carburetion
Since the 845 has such huge bores, it also has more “inlet signal” strength than any other SuperJet engine package ever built. In layman’s terms, inlet signal strength is the actual vacuum that the crankcase uses to draw fuel through the jetting circuits of the carbs. This vacuum is generated by the movement of the pistons Having a lot of “signal” is a big advantage, because stronger signal results in less temperamental carburetion, and less fine tuning for changes in altitude and weather conditions. The strong signal of the 845 kit allows very precise jetting of nearly any carb you install on it, and it will very little fine tuning for changes in weather conditions.
The stock SuperJet comes with dual 38mm SBN Mikuni carbs. Group K routinely modifies the throats and jetting of these carbs to increase air and fuel delivery for modified engines. These modified throat 38s are a very popular alternative for 701/760 SJ owners wanting to get the best of both performance and fuel range, and they also work very well on the 845 kit.
During our testing, we also used the larger 44mm carbs (and manifold) that comes as original equipment on the 760 Yamaha engines. While these carbs are a bit too large for the 760cc application, they worked perfectly on our 845 prototype. Since there is such a big focus on getting enough fuel and air to the 845, these oem 760 44 carbs are a very practical and effective choice for owners that want to get the most from their 845 kit. Unfortunately, the 44s do have considerably higher fuel consumption than the modified throat 38s. Given that, owners who have a high priority for fuel range should defiantly fit their 845 with the modified 38s.
cookerq62
Life's Been Good
- Location
- Upper Bucks, PA
That sounds like an awesome motor package considering you don't have to buy any expensive parts other than a b pipe. Unlike alot of the other 800cc+ packages you need a head, carbs, crank or cylinder, and ignition for. Do you know how many overbores can be done and what kind of pistons it uses?
matt that is not true, you have to have the cases ported and epoxied by someone who knows what to do. i have run ported an epoxied cases for years turning 7800 rpms for 20 minute motos. you just have to epoxy with something decent not jb weld. we usually marine tex.
plus the cases i got from you had crappy epoxy that fell apart and there was a crack in the front of the cases behind the epoxy that was causing the air leak. i am not complaining at all, you could not see the crack until all the epoxy was removed.
my point was ported cases just provide more airflow, the epoxy is used to restregthen the ported areas.
OK well sweet. Because I did notice the diff in those cases! Those things were heavily ported and they ripped!!
I guess I would do it again then if it was possible to make it permanent but I would still just prefer just slight machine work just to clear sleeves.
Sorry about the crack! Did you weld it up and run em?
I guess I would do it again then if it was possible to make it permanent but I would still just prefer just slight machine work just to clear sleeves.
Sorry about the crack! Did you weld it up and run em?
From what I understand it is that bore and 1 more and done. But I have had motors last 6 seasons before so if I get 6 to 10 summers on cylinders I am happy.
I have everything he requires except I have a mod pipe. He said it would be fine but more bottom with limited.
I'm really diggin this package.