squish parameters and jetting

[new250r ider]

Hey guys - need help bad. Bought a 250r with the head and cylinder top recently shaved but the guy didn't know how much was taken off and he hadn't done a squish test before hand. He has 3 gaskets under the cylinder and compression is only about 95psi. Anyone know what the squish should be? Compression? Also need a ballpark on jetting because the guy sold it due to burning out pistons in a hurry. Running fmf pipe, boyesen reeds, no access to racing fuel. Thanks

[jhtrx250r]

burning pistons on a 250r? sounds like someone messed up the port timing or jetting is way off.
My advice.
If the top end was modifyed (3 gasketsunder the cylinder ?)
then buy a good stock cylinder and head start with a new piston, set the carb back to stock jetting and then ride it get a feel for a good running bike and do all your mods from there.
dont wast your time on someone elses messup/problem
OE 250r top end parts are easy to get and fairly inexpensive.
And you could drive your self crazy chacing problems if you have no idea what the history is
also 95psi not enough to run (well at least run worth a damb)

[new250r ider]

yeah, thanks. I kind of thought that might be the best bet. I was just hoping to get it running and work on jetting to see if that was his problem with the pistons but I don't know if the compression is so low because he spaced the cylinder up too high or what. I talked to one guy that said he thought the squish should be around .065 but he wasn't sure, and this one is about .102

[wilkin250r]

0.102" is huge, even 0.065" is really big.

The cylinder head is cooler than the rest of the intake charge, so any fuel/air in contact with the head gets cooled. But the further away from the head you get, the less effective this cooling effect is.

Ideally, your squish should be somewhere around 0.035". Significantly bigger than that, and you reduce it's effectiveness in reducing detonation.

[86 Quad R]

when you say it has 3 gaskets under the head. do you mean it has the three layer thats in a single peice or what? from the factory, the 250R's squish band @TDC (distance between top of piston to head) can vary from .075 - .125 as mentioned, the ideal squish band should be no less than .035.

[new250r ider]

no - he actually took 3 factory gaskets and stacked them up.