Question about 2004 Yamaha YZ 450 F
I crashed and crunched my exhaust at the end piece.. its pinched pretty good.. i kept riding for the rest of the weekend. the next week it started then i shut it down.. when i went to restart it it was locked up.. take the spark plug out spins freely. so we know its a valve problem.. did the shims and it ran fine for an hour.. shut it down and it locked up again. the only thing i can think of is that the backpressure from the pinched pipe caused to much heat and warped or bent a valve? The only thing i can see wrong is a ex.valve is stuck closed.
Take off you valve covers.(circle covers on head) then take off your crank case cover on the side of the bike. put a scoket it and spin it over and check and see if your cams are engageing your exhaust valve. there more than likely gonna be engageing. but if its warped ull prolly be able to see it. but if not just spin your crank untill your exhaust valve is or looks completly closed then poor a lil 2 stroke oil or gas on the valve if its warped the oil will seep past it, if its closing it will not, id use the 2 stroke oil because you can see it. but gass works. never use water or anything like that, gas and oil are fine because the engine uses it any way.
but who knows maybe u busted a oil gallery and it seaized, having nothen to do with the valves but any way i hope i helped. its hard t say when i cant physicly see it
Posted on Nov 13, 2009
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Posted on Jan 02, 2017
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