Any body have any advice on this? I know the big bore kits with ProX cylinders work great but I hear that there can be overheating problems when using a stock cylinder with this kit. The quad is an '89 250r that is going to be used for flat track racing. I want to keep the motor looking stock so I'd like to use the stock cylinder. If you've done this or know someone who has I'd appreciate any and all input.

Thanks.

John

 

DONT DO IT I HAVE NEVER SEEN ONE THAT RUNS FOR VERY LONG. THEY HAVE A PROBLEM HOLDING HEAD GASKETS AND THE STUDS IN THE CYLINDER ARE TO CLOSE TO THE BORE AND WHEN YOU TIGHTEN THE HEAD IT DISTORTS THE BORE AND YOU LOSE COMPRESSION. YOU WOLD BE MUCH BETTER OFF WITH A AFTERMARKET CYLINDER OR YOU CAN GO UP TO 69.5 MM IN YOUR STOCK CYLINDER WITH A 86 250R PISTON AND A SPACER PLATE.

 

Thanks for the input, I think I am going to run the 69mm piston (270cc), I wanted to run the 295 in a stock cylinder because I'd like to run 250cc and open classes and I know the aftermarket cylinder will give me away.

John

 

some builders can hide a stroker in a stock cylinder with custom head. getting a custom head with orings is the way to go.

 

I run a 295R big bore kit and I have NO problems with keeping the coolant seperated from the combustion chamber.

I use a 2- O ring set up which works awesome.

The bore does not get distorted when you torque the cyl head down.

If the top of your cyl. is perfectly flat and also the head surface you will not have any problems.

 

You can try LRD they have a 300 kit, using the stock jug. The same as Bill Ballance uses, I haven't seen on though it sounds reliable.

 

You should check out the Vitos big bore kits. Um, MTAwest (motorcycle tires and accesoriess) carry's kits. www.mtawest.com