how do I do a compression check

[custom R]

What is the right way to do a compression check should I hold the throttle wide open or closed and does it matter if the threads on the guage are shorter than the plug

I have about 160 psi with a 20 cc dome and a stock trx gasket with the throttle closed when i kick it

Im wanting to get to about 180 psi so do you think a cr gasket would get me there or should I try a 19cc dome

thanks for the help and also what is the stock bore on an 87 mine is at 67.5 and i was wandering how many bores I have left & what cc's is 67.5

[deathman53]

if you go with a cr gasket it will bring you to around 190, you can also get more compression with a 19 or 18cc dome. and as with the bore, you have a 258, you have 2 more bores on with the 87-89 piston and can go to 120 over on a 86 piston. If you have a long rod, you need a spacer plate to use 86 piston. For the compression test, hold the gas wide open.

[AtvMxRider]

Hold the throttle wide open and kick it until the guage stabilzes(about 20-25 times)