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GRRRRRRR!!help

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I just rebuilt this 2002 yz250f...new piston ,rings,cylinder new valves,springs,seals everything brand new...i started it up,,,idles fine....give it gas and it makes like a high pitch wizzing noise around the head and now when i kickstart it has compression but not a lot...i dont have to really kick to turn the motor over....please help if you know anything...im so frustrated:banghead: :D:worthy::)

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Squeal, wheeze, hissing is usually either leaking valve or blown out head gasket, or like mine did the other day, a loose exhaust header flange. Sounded like a tractor going down the trail when I let off the gas. Check the head bolts, make sure you don't have water in the oil, or oil in the radiator, then double check the valve clearances.

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Question.... does it have the '03 or newer, or a HotCam exhaust cam in it? The cam will bleed off just enough compression when kicking to make it easier to start. Only other thing is tight valves will make it loose compression or items I mentioned above. Only other way to check it is a leak-down test.

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u are really having a tough time with this bike, whizzing noise could be the timing chain, the guides worn down to the metal in any spots, also the cam cahin could have jumped a tooth causing the bike to have low compression.

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OK. Where are you at ? Bike starts and runs ? Does it rev properly ? Asumming all is corect. You checked valve clearance, Timeing is correct. Plug is tight. Its ussualy the simple things. Exhaust ring put back in. Did the cam chain guides slip off thier index? Release the cam chain tensioner?

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