I purchased a 99 yz400f one month and a half ago. Loved it, but it now has a bad engine. Here is what I know. It had a top end rebuild about six months ago. This was done by the shop I bought the bike from. I rode the bike a couple of sunday evening and 15 to 20 minutes after work a couple of days. I am being told it has worn bearings on the crank. I guess what I want to know is average cost to repair. I am stuck now, so I have to fix this bike or waste the money I have invested in the bike now. It never had any knocking or starange noises, on the the day it broke, I was riding it powers off and went into a slide. I was able to restart, but the same thing happened again. I deccided to put it on the trailer and take it to the shop. Any Ideas on whats going on and what it cost to fix.