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View Full Version : Pulled apart motor, valves are hiting piston



Lquad71
01-09-2012, 12:26 PM
So i pullde apart my motor to send in the head to get rebuilt and when i took it off i noticed that the intake valves are hitting the piston and it just started. (piston is only a 12.5:1) My motor builder said that when we took it in for a noise he said the crank bearings were bad. could this be it? also, the cam seems to have abnormal wear on the contact area of the lobes. Can i get my cam rebuilt or plated, because i dont want to go pay for a new one like this.
One last thing is there are some score marks on my cylinder. not many, but there are some. the most of the marks are on the intake side. any help is appreciated.

400exrider707
01-09-2012, 01:46 PM
Either it was over-revved and there was valve float, or the timing was off...

I can't imagine crank bearings going causing the piston to hit the valves, especially if it's only 12.5:1.

What do you mean by abnormal wear on the lobes? Describe this a little more or get pics if you can. I mean if the valves were hitting the pistons due to a mechanical issue like timing jumped, then it would probably put more strain on the cam/rocker faces as well. What kind of cam is it? It may be cheaper just buying a new Hotcam or something.

If the cylinder is scored and it's down for rebuilding, just buy a new cylinder, they were only like $190 from Honda last I checked. Boring and re-plating will run more than that for sure.

JH Racing
01-09-2012, 03:03 PM
Also check and make sure the flange did not spin on the cam