Okay, i have an 04 400ex and i am thinking about dropping in a wiseco 10:1 compression piston. My question is if i do go with the 10:1 will i still be able to run on pump gas (93)? And if not then what octain would i need to run. Maybe 110? Also i am a do it your selfer and i have rebuilt my 2 stroke dirt bike several times, but have never messed with a 4 stroke. Is it hard to do the pistion swap on a 4 stroke by your self? I do know that i will have to get my sleeve honed to match the new piston, i believe it's 1.00 mm bigger then the stock bore. Has anyone out there done this, and if so where they happy with the outcome? Was there is big diff in power? Do you think its worth the trouble? Thanks ahead of time.

 

One mill over would go to 406cc. It would be a good mod. You could still run pump gas no problem. The only real difference in working on the 4 instead of a 2 stroke is the cam and valves. If you have done a 2 stroke with the manual from the bike shop you shouldn't have a problem swapping the piston.