for those of you wondering about this certain mod i have some info for you .
the one i have been working on uses a kawasaki flat top piston(kx500 86mm) with a steel sleeve and the aftermarket billet power valves . do do this mod you need to have the cases worked to acept the larger sleeve and the cyls as well. the wristpin hole need to be drilled a little larger to accept the yamaha wrist pin but all in all the kawi piston will fit well. the issue i came across is the powervalve , MAKE SURE THERE IS PLENTY OF POWERVALVE TO PISTON CLEAREANCE ! the radius of the valve will need to be matched to the radius of the bigbore pistons and then you need to set the clearance . there is a lott of manual labor along with machine work when doing this so if your wallett is light dont even think about this route of modifications .
i hope to have this setup on the water soon so ill keep you posted on how it turns out.the boat being used is this:
2001 gpr
factory pipes with stinger inserts
factory pipe water box with water injection
dan lamey big bore set up
buckshot carbs
dominator intake
m-16 reeds
cases ported
cyls ported
advent cdi
riva pro series heads
12 vein pump
impros pitched skat prop
and all the handlig goodies as well. the motor dyno'ed at dans at 240 hp @7400 rpm , so time will tell what this will do on the water . the only thing im wondering about is the lower rpm to hp number because from im being told the motor is supposed to spin at 7800 , thats 400 hp more than peak hp , so what is the hp at 7800? should i bring the rpms down with a steeper prop? ahhhhhh , time will tell !

Dana We recently put together an R&D 86mm Big Bore which we are running fat until the mod Buchshot/R&D carbs go back in.

R&D sleeved the cylinders and machined the power valves for proper clearance, but we did not have to machine the cases at all. We are using 86mm Wiseco's made for R&D.

We will post info and pictures once the project is complete.

Good luck on your project

Fercho

Fercho is your project triple piped?

fercho,
run the engine for 1 hour then pull a cyl and look at the side of the piston . when this motor was originaly assembled the builder though he too put enough clearance between the valve and the piston but there was not. thats why im redoing it.
the great thing about the kawasaki pistons is that they are made by ART and cast so they will last longer and will be more rec friendly . the valve was originally set at 30 thousands but like i said it needed a lot more than that.

Dana,
I went with the same setup from Dan L (Flat Tops +sleaves). I used the R&D valves. I had my machine shop take off +50 thou inside off the sleave. this gave me a decent amount of space. The motor is runing extremly strong 1/4 to wot. Idle and bottom end runs real rough. I'll be pulling the motor apart to check reeds. Do you have pics of the underside of your pistons? As i drilled Dan about the cases. He said they will be an issue?

Pat

WB800Blaster.........So are you saying that Dan Lamey doesn't know how to build a Big Bore for the GPR?

Yikes!!!!!!

Guess he better just stick to "reliable curves for Advent" huh.

Drink My Dust,

after i re read what i typed I see where u are comming from, I meant on the PV's i took extra off passed the sleeves. Mine runs great, Dan did great job, I have another on its way to him. I ve read a few posts about the cases needing to be re done, i yet to see pics of damage mor what soud it makes.

so how are these boats running these days?