Spark plug and Compression

[6988june]

i am putting a 13.5:1 JE piston in my bike, should i adjust spark plug for this or stay with stock? Also I am going to do several compressions tests during break-in, any word on about how many psi i should be at? Any help is appreciated! Thanks

[dirtman91386]

what ever stock is (142 i believe) plus 4-7 lbs for the piston plus maybe 1lbs for the gasket, cams also play a roll how much compression you get on a tester...the more aggressive cam the higher compression, the more octane you will need to keep it from detonating