View Full Version : I think im losing power
400exmxracer
04-25-2013, 08:37 PM
So, I completely rebuilt my motor over the winter from the bottom end up, and its starting to feel like its not pulling as much when im riding. I don't know if its just because I'm getting used to the power, or something else. Please give me some ideas of things to check for slight power loss. Thankyou.
Check your compression. 100psi minimum.
400exmxracer
04-25-2013, 09:06 PM
I have a wiseco 11/1 426 piston. What should the compression be?
Like I said, at least 100 psi.
Zakradu398
04-26-2013, 07:22 AM
With an 11:1 in my 400ex when it was brand new I believe I had slightly over 200psi
JOHNDOE83
04-26-2013, 10:11 AM
My 440 after some usage had 165psi when I installed my stage 2 cam.
Like they said above 100psi minimum, that is the baseline for any bore.
Blodg
04-26-2013, 02:25 PM
I have not done a compression test yet on my 400EX but wow those numbers seen low. On my full race 492cc 350X motor I measured 270-280 PSI and on my mildly built 355cc 350X motor I measure 225-235 PSI. Or maybe my gauge is off? I will measure the 355cc motor again and then measure my 416EX after break in.
Those 400EX numbers are with the decompression removed right?
Zakradu398
04-26-2013, 04:54 PM
yea, it could have been a little higher also due to extra oil in the cylinder when I put it back together.
Highest I ever read on my 426 was like 180psi. But baseline is 100 psi, anything around 100psi or lower needs at least rings.
KKiowaTJ
04-26-2013, 07:37 PM
I dont know what kind of build you have, But maybe the clutches are too week. The warm weather possibly? Thus motor running warmer needing a thicker/different oil.
I have always noticed that no matter whos quad/bike it was, It always ran harder in the cooler riding seasons. Good luck either way
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