Group K Sleeper Kit

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MPower

MPower

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Been a pretty miserable summer recovering from ACL surgery. Need to tinker with something to pass the time. Since my motor let go at the Norman ride I have this spare motor I need to get ready to install once the knee is ready.

I'm considering sending the cylinders to Group K for their rec porting and the carbs to have the throats bored.

Anybody have experience with these two mods? I prefer to stay stock pipe and this setup is what they consider a maxed out stock pipe setup.

Worth it or no?
 
I had my 97' XP done in 97' when it was 2 months old and went for their full Sleeper kit. The only thing that gave it away was the R&D air cleaner. It was everything they said it would be and never had a single issue. I sold it years later to a 18 year old girl that didn't have a clue and never saw it again.

After the sleeper kit I was dead even from top to bottom with the 98' XP Limiteds when they came out.
 
I have two sets of GroupK true bore 40mm carbs, a GroupK cut head in perfect condition, many flame arrestors to choose from, etc.
 
So if you want more top speed, you need raise your rpm...stock pipe peak is 6900rpm...i am not fan cylinder ported...i prefere raise the psi, flame arrestor, skat trak swirl,..with stock pipe....if you want more, put aftermarket pipe and aftermarket carb
 
So the Sleeper Kit is also many of those things:

Porting
Cut stock head (170psi?)
True bore stock carbs and jetting
F/As
Hard jet waterbox
85/88mm nozzles

Harry advertises 62.7 mph at 7050 rpm with this setup, not bad if true for $595

7300 RPM and a FR pipe would be nice but I want to run on pump gas.
 
That is not completely true. With more power from all the porting and other work you can pull a higher pitch impeller so even with the rpm staying at 6,900 max you can get higher top speed.
That is why you don't have to spin the motor higher at the cost of crank bearing life.

Also keep in mind that Group K focuses on endurance racing not peak top speed. A Factory pipe might make a little more speed but it is at the cost of crank life and possible higher octane fuel. Also our resident performance parts guy Matt B. says that you can't feed enough fuel into a Factory pipe with stock carbs so that is another expense.

Group K has done their homework and even re pitch aftermarket impellers to exactly match the engine work.
 
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mikidymac said:
That is not completely true. With more power from all the porting and other work you can pull a higher pitch impeller so even with the rpm staying at 6,900 max you can get higher top speed.
That is why you don't have to spin the motor higher at the cost of crank bearing life.
Click to expand...

Yep, exactly.
 
GroupK has been there from the beginning and their machine work costs are reasonable. I believe the kit will be worth the money but 62.7mph? I don't think so brother. Not on pump gas not even with a light rider and a quarter tank of fuel or less. I've thrown every part ever made at them and don't quite get that. I am pulling big sponsons and scoop grates though.

I hope I'm wrong and I'm not calling Harry Klemm a liar. I just think that must have been a hundred pound rider with the wind at his back running on fumes in a 95 or 98 hull with a one mile an hour current under him running in his favor.
 
Oh I've definitely been in the sport long enough to realize those numbers have to be taken with a grain of salt as they were achieved in the perfect conditions under perfect circumstances. I've installed many "kits" for people and seen very few run the advertised numbers.

My 95 has run 59.9 on GPS consistently so another 2-3 mph seems possible.

Main question in all this is the porting and carb boring. Are they noticeable gains worth the money? And gains can midrange, not just looking for top end.
 
In mine the biggest difference was in the low end and midrange. That is where the stock 97' XP was a dog. The Sleeper kit made a huge difference, like I said, I was able to keep up with the 951 Limiteds.
 
I use few years, porting and 40mm...yes big gains mid range and 1 top speed mph..
 
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Matt Braley said:
GroupK has been there from the beginning and their machine work costs are reasonable. I believe the kit will be worth the money but 62.7mph? I don't think so brother. Not on pump gas not even with a light rider and a quarter tank of fuel or less. I've thrown every part ever made at them and don't quite get that. I am pulling big sponsons and scoop grates though.

I hope I'm wrong and I'm not calling Harry Klemm a liar. I just think that must have been a hundred pound rider with the wind at his back running on fumes in a 95 or 98 hull with a one mile an hour current under him running in his favor.
Click to expand...

FWIW, my 95 GTX dropped 3 mph when i went from stock sponsons to beach house on the most aggressive setting. stock motor @150psi, stock prop, dr. honda carb rebuild. handled like it was on rails though.
 
A Spec 2 can be pump gas safe. I would not run it in conjunction with a cut head though. The pipe itself has more in it then you would want to take. You could flow more water through jetted fittings and keep your carb jetting on the rich side while even retarding the timing a notch. If it over revs then you can have the impeller pitched forward or use smaller nozzles to get that sweet spot around 7200ish.

I believe in the benefit of cylinder porting. However there is a lot more room for improvement in post 95 787's. More time was taken to make smooth transitions between the sleeve and the cylinder and the exhaust ports are slightly higher in the 95's. It's possible someone could have cleaned this up in the past but look at these 95 intake ports



 
My exhaust porting was open 200 duration exhaust! But this porting was not the best.. To high for stock exhaust..
 
Great info Matt, thanks!

The spare motor I have is from a 96 so even more reason to have some mild porting done to get it closer to my 95 motor that let go. Although the cylinders may be salvageable.
 
Wow Matt. Those 95' cylinders look nothing like the stock 787's I have seen although I have never has a set of 95's either. Those look great. All the 787 and 720's I have seen have pretty poor port matching and are raw castings not like the polished ones in your picture.
 
MPower said:
Great info Matt, thanks!

The spare motor I have is from a 96 so even more reason to have some mild porting done to get it closer to my 95 motor that let go. Although the cylinders may be salvageable.
Click to expand...

so you're thinking of sending off the spare motor to get reworked and just remove and drop in when the new motor comes back?
 
mikidymac said:
Wow Matt. Those 95' cylinders look nothing like the stock 787's I have seen although I have never has a set of 95's either. Those look great. All the 787 and 720's I have seen have pretty poor port matching and are raw castings not like the polished ones in your picture.
Click to expand...

Yeah that does look a little better then stock I guess. This motor had a billet head on it so someone probably did some clean up work in there. It ate something and won't roll all the way over so I have to tear into it. I'll probably set those cylinders aside for myself.
 
mikidymac said:
Wow Matt. Those 95' cylinders look nothing like the stock 787's I have seen although I have never has a set of 95's either. Those look great. All the 787 and 720's I have seen have pretty poor port matching and are raw castings not like the polished ones in your picture.
Click to expand...
Per the 96 race manual the 95 cylinders have different port timing than the later years
 
I don't doubt that but those ports look like they were really cleaned up. I haven't seen any 95 cylinders but as the 95' s were made to keep within the racing production rules and were bored oversized from the factory I could see them cleaning up the ports too.
 
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