mooney26
Veteran
What is the compression on a 2006 stock APEX motor? I have a FPP turbo and last year added head shims to lower compression and run on pump gas. This year installed yamaha's low compression pistons and has dropped compression down to 95 across all cylinders. Does anybody know what stock compression is and what the low compression pistons typically drop compression too? 95 seems awefully low????
ranger1
TY 4 Stroke Guru
Not sure what the actual stock compression is suposed to be but I just happened to check mine today & I got 140psi, 140, 140 & 133 on my gauge. Not sure why the last one is %5 lower than the other ones though.
TurboTime
TY 4 Stroke Junkie
mooney26 said:
What Pistons did you install? 9.5, 10, etc... Makes a difference on comp gauge.
Riceburner
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mooney26 said:
My 2006 GT was between 180 & 188 when I checked it after 2 years.
copo427ss
TY 4 Stroke Junkie
i believe the ratio was 10:1 or 10.25:1 stock. are you holding the throttle wide open while cranking the engine over while checking cylinder pressure? it makes a difference. also make sure your cylinders are wet (a little fogging spray or wd40).
teamyamaha
Extreme
Each compression gauge may read differently, try two if you can get you hands on another. Wide open throttle, I personally test with the engine at operating temp.
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