10:1 or 11:1 piston for 400EX
#11
#12
#13
from the factory, there is a difference. the center gasket is much thinner on the xr400 headgasket, this is how it is 1.5 points higher. the aftermarket probably just uses a xr400 style and runs with it, maybe that is how they sell the piston as higher compression by swapping gaskets. I put a xr400 gasket on mine and it made a difference.
#14
Air hit it.Good to see another wrench in here who knows the bolts.Just to give you guys a better idea look at the yz426.It has pretty agressive cam,12.25 comp piston and it only needs 91 octane.My bud just got a new 00 yz426 and runs premium 92 in it with no probs.This Is Calif gas also,very loaded with crap.remember higher octane rating means gas burns slower to prevent detonation.Only run as high as you need so it doesn't ping,anything higher is useless and actually will hinder performance due to incomplete burn.
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exmotocrosser
Polaris
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09-13-2019 06:12 AM
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