My son brought home a 450f basket case!

Where would the needle bearings come from if it broke a valve spring retainer cap?

Trickle down damage affect.

broken valve retainer = dropped valve = piston thrust into dropped valve = sudden bind on bottom end bearing when everything (piston/valve/head) crashes together. The rod can also be slightly bent.

Needle bearings may not have detectable damage but hairline cracks will come apart in a short time.

I bought a 2003 YZ450 a little over two years ago in boxes...had a seized crank bearing, which I'm told was common for the year. Put in a new crank/bearings, put it back together and have raced it for two years without touching a wrench to it other than routine maintenance. Just got the head back from MX Time and rode it three hours yesterday and it runs stronger than ever. I would highly recommend MX Time for head work...there is a needle bearing at both ends of the crank. I would replace them if you have the motor out and apart anyway...especially on a bike of this year.

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