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400ex 12 to 1 JE piston

240 Views 3 Replies 3 Participants Last post by  Domains
I have a 06 400ex I was running a wiesco 11 to 1 piston blew up and was wondering if I could still run 93 octane pump fuel with a 12 to 1 piston? Also how good are JE pistons never Hurd of them? Thanks
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You should not be running pump fuel (mixed with alcohol), but if you can get 93 octane non-ethanol blended fuel from the pump, then it will be fine with a 12:1 piston. My CRF250 is 12.9:1 stock compression and calls for 93 octane - I found out that at 94.5 octane the engine suffers a loss of power. I have been running 91 octane non ethanol recreational gas and have no problems with either spark knock or detonation.
Why not put a 91 piston if you can get it, alot more power
I placed a xr650L in a 400ex with a big bore 91 piston, scary power
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