Should I Replace My Yamaha ATV’s Crank Along With the Head?

If you’re rebuilding the top end of a Yamaha YFZ450 ATV’s engine, should you go ahead and replace the crank before putting a new head on it?

Partzilla’s Yamaha ATV expert John Talley hosts live Q&A sessions on our YouTube channel every Friday at 3pm Eastern. In this session, John was asked if he would replace the crank before installing a new head onto a 2009 Yamaha YFZ450 ATV.

Yamaha YFZ450R engine rebuild

Yamaha YFZ450 Crank Replacement Q&A

I finally got going on my 09 Yamaha YFZ450R. If you were doing a freshly built head (ported, cam, and a bit higher comp), would you replace your crank before slapping a fresh head on?

John Talley: I know that machine pretty well. Not if it measured out right. I would not disturb the bottom end. The cranks on the 450Rs, especially the 09s, are really solid. I think we’ve gone through three top ends now on my son’s YFZ450R, but yeah I wouldn’t mess with it. As long as it measures out right as far as it’s in play, I wouldn’t mess with it. I would just keep going.