2005 YZ450F Engine Help

I recently bought a 2005 YZ 450f it had about 6 hrs. on it but had been sitting all that time with gas in the carb. After cleaning the carb countless times with no great sucess, I replaced all the jets and float. The bike starts and runs very strong but makes a lot of engine noise, has a bad vibration and back-fires. Also, the header pipe right out of the engine gets extremely hot 15-20 seconds after starting. I drained all the oil and checked the filter. The oil was brand new without a trace of metal. I pulled the side cover and clutch off... it looks like it had never been started. I also checked the valve clearance and that was fine. WHAT THE HELL IS WRONG WITH THIS BIKE!!! Can someone help?

Usually engine noise is the rings going bad, when it gets really "rattly" it's the piston slapping the head/valves...Might be time for a new top end?

Hopefully, you got rid of the old gas. It was more than likely worthless after that much storage time. Backfiring from the exhaust on decel, and some of the header heat, may be a matter of nothing more than an incorrectly jetted or adjusted pilot circuit. But a good deal of the hot header is normal, too, and it's not abnormal in the least for the pipe to glow a dull red after as little as 30 seconds when viewed in low light.

Likewise, an unbelievable amount of engine noise is also quite normal. On that score, your best off comparing yours to another similar unit known to be in good health.

Spend some time browsing the fuel system section of the Common Threads/FAQ's sticky at the top of this forum for details on adjusting the pilot circuit.

I have A 2000 yz426,and the amount of noise it makes close to the cylinder while running is down right scary.Been riding it every weekend for 6 months and everything fine oil looks good when I change it.little bit of metal in filter but heard that is normal also.

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