Originally posted by whynot
I have a question I have a brand new jp .21 worlds motor 2002 and I will be running 20% odonnel fuel.How much shim thickness should I have?I think it has around .5mm -.54mm in it right now.also how many different thickness shims are there? thank you very much.
mike wannett
Depends on where you get your engine from. If you get it from U.S through authorized dealer then it should come with 0.6mm headshim (shim for 20%).
I was told if you get it directly from Europe, then it comes with 0.4mm (for 16%).
I run mine at 0.7mm head shim just to be on the safe side.
Just FYI, it you dont haev enough head clearance then it will be over compressed and you will crack your piston or suck a plug in there!