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2008 xc-f 250

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have 2008 xc-f 250. Bought it brand new, never raced, taken care of it to the T. Motor lost power and then shut down. Parked it and let it set for a while. Motor started up but was tapping. Investigated and found the left side as you sit on the bike cam lobe and bridge assembly had completely burned up. Motor was pumping oil fine everything clean. Tore down motor to the piston. Replaced the rings, cams, bridge assembly, gaskets, and tensioner. Checked tolerances on eack valve, all were at spec. Closed up motor and kicked over severasl times without plug to get oil pumping which was visible in sight glass. Installed plug and fired motor, motor sounded and idled fine. Shut down and double checked fluids. Re fired and bike went 9 miles and did the same thing. Did everything to spec with support from dealer and very experienced other mech. Appears the one cam surface is being starved of oil but we have no idea at this point and no one else has heard of such a problem. Intake cam burned up bridge assembly melted down! I need help!

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Sorry to hear of your double bad experience with the engine. Did you pull the valve cover and see the oil bathing the cam? I am no pro, but I would guess that you have a block in the oil passage running up to the cams. Or one or both of the oil pumps are bad. I dont think you have the plastics oil pumps like the bigger bikes, but I am not for sure. My mechanic has stated that the plastic parts for the oil pumps have failed in the bigger bikes.

I know nothing!:thumbsup:

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yes we made sure oil was coming out of oil jets. Everything was getting oil but at some point it appears to be failing or losing pressure

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Is there anything in the top end that could be rubbing the cam and wiping the oil away?

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