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markvan

stiff cams....

7 posts in this topic

Right now I've got the engine apart, and am putting in new rings. When I' put the head back together one cam seems to roll freely like it should the other is really stiff as soon as I tighten the bolts on the cam bearing cap. Even just finger tight and cam is binding somewhere..... I have only taken the cam bearing caps, and the cam locating rings, and cams out in order to get the head and cylinder off....so I didn't touch the valves at all. So there isn't much to put back together and I can't see what I could have possibly done wrong.... Any ideas guys? :thumbsup:

Thanks, I hope this can be resolved quickly as we are leaving for a 6 day riding trip next week and I need my bike together soon!!!!

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I just rebuilt the top end on my '03 yzf450 and had the same problem with my intake cam. The exhaust cam spun freely, but the intake was really tight. I had a bunch of people look at it, but nobody really had any answers, so I put it back together like that. I just fired the bike for the first time and the bike seems to run fine so far. I'm not sure what would cause this. Anybody have any suggestions????

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Is the engine on intake stroke and the cam pushing valves open?

If the bearing surfaces looked ok, valve clearance correct, and the bearing caps are torqued properly, Run it!

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i had the same thing,,,i talked to one of the mechanics for yamaha of troy and they told me to go ahead and run it they will seat in themselvs

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The cams, intakes in particular, seem to run very close clearances in all of these that I have seen. My 250F is fairly snug, even though the clearance is in spec. (anybody ever try spinning the cam in a V-8 by hand?) If there is no scoring on the shaft or in its journal, and you haven't done something monumentally silly, like tightening the bolts without a torque wrench or all in one step, it's probably fine.

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This happened to me and it took a little while to figure it out but this is the reason. When removing or replacing the cams, sometimes, like allways, the cams will hit the bearing surfaces and scrach or ding the bearing surfaces. All you need to do is get a little scotch bright and take the inperfections out and the cams will run like free willy. This is no Bull*&$#

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I always polish the cams till they spin freely... alittle bit of emery and the lathe will fix it right up. If they are binding or dragging something is wrong. Possibly improper torque or whatever, but they shoud spin freely. Tdub

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