YZ450F ringing when hot

Joined
Oct 3, 2006
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#1
Got a mate that rides an 07 YZ450F. Regular oil changes, synthetic oil, valves appear to be in spec. When the engine gets warm, there is a slight ringing sound as the bike is revved. I'd say the performance of the bike doesn't decrease, just that the ringing increases. Any ideas of why?
Also, I want to put a high compression piston in my YZ250F. I was told that I need to run race fuel to do this. However, the 08 Yz250F already comes with a high compression piston but does not require race fuel. Do I really need race fuel if I install a high compression piston on my bike? Thanks for any feedback given. DRN rules.
 
Joined
Jul 27, 2007
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#2
Is it a pinging that you hear?

Try running higher octane gas and see if it clears it up.


As far as your 250, try running it with pump gas, if you hear it ping then run higher octane race gas.