Originally Posted by CrazyD2.0
When I ordered the engine gasket kit, I did get the various thickness gaskets. I set up the height according to the engine manual for the 250, which called for 1.2 to 1.3 mm from the top ring land to top of cylinder. The manual warned that too short a distance would cause "pinking" which I take to mean running too hot and causing pre-ignition, and of course too high would lose compression and power, but I didn't know that there would be an acceptable range. So I set according to the spec.
I think it varies on different KTM's,I had an 04 MXC250 and guys go as far as to use the piston/head from an SX model to get compression to where it should be,otherwise they are weak off the bottom rev zone.
Ive got an 09 XCW 200 now and guys run thinner base gaskets to get more low end out of them.
KTM has the X factor which is exactly where they want cylinder heidth set at.
Guys do experiment some and compression can be checked once its torqued down,160/170 psi would be good.
Id love to have a good running 1980 420MC,they are a sweet running smooth big bore.