yz426f high compression piston

[kelticsean]

i was wondering if i could run a 13.5 to 1 compression piston with hot cams stage 1 cams in a 2001 yz426f? will there be any valve clearance issues?

[Birdy426]

Plenty of clearance on my 426...uh...444. I would still advise doing a "clay check" during assembly just to make sure, but I had about .055" to the valve on mine.

The power is awesome. I went up one tooth on the countershaft sprocket on my WR (already geared taller than the YZs) because first gear wouldn't hook up, it would just dig trenches!

[LukeYZ426F]

i had a 426 bored out with the hot cams and 13.1 piston... eerything fit fine. Go ahead and start excersising that right leg. Ive NEVER had a boke with so much compression. i could stand on the kick start with ALL my weight ( all 225 pounds!) and it would move. iif we were out riding and id lay the bike over and flood it i wouldnt even try to kick it. Id start walking to the nearest hill so i could jump start it. And when you jump start it youd have to be in like 4th or 5th gear so the rear tire wont lock up. The power is great though, even my 525 couldnt compare.