Yesterday a friend of mines 250R blew a hole in the top of the piston, He already had his cylinder decked and exaust ported from a previous rebuild and he would like to know what other 250R owners have done to their machines in past rebuilds that they were very pleased with. Any info you can give on Pistons, Ram valves, etc..... that have worked good will be appreciated.
He would especialy like to know about any possible pistons other than Wiseco

 

Hello fello R owner, first of all its not the pistons fault. He's either running to hot of a plug with a lean gas mixture, a exhaust leak right at the head could also be the problem. If the donuts are bad then the engine is sucking to much air! I had the same problem with a tecate of mine, it had too hot of a plug (my fault) with a exhaust leak right off the pipe, I had just re-built the engine that weekend and kaboom, burned a hole about the size of a dime right through! Hope this helps.

87' "R" Stock except maier plastic, fmf pipe.

99' 400ex, +2 burgaurds, Axcaliber +4 axle, Works triple rate front, ultracross rear, WB E-series full system, DG nerfs, Race Bumper, Full skid, Nacs block plate, Maier race plastic, jetted, WB high flow air cleaner

 

There are several possible causes, here are the most common; air-leak at the stator side crankcase seal, too lean carb jetting, faulty ignitor box or too far advanced timing, too hot of a spark plug range, too high of a compression ratio, or too low octane fuel. Without specifics on exactly how the motor is set up it would be hard to determine. I would make a guess that it IS either the plug range or the JETTING. About the Piston delimma, I would personally recommend the cast PRO-X piston. The cast pistons seem to be much more forgiving than the forged pistons when considering warm up times and jetting. Within the last year I went from the Wiseco to the PRO-X, and actually PREFER the PRO-X.

 

I did forget to mention that he already knows what burned a hole in the piston, a combination of too hot a plug and not high enough octane in the gas.

 

hes gonna have to start running race gas i run 110 cam2 my bike runs great with it but its still abitch paying 5.00 a gal