04 YZ450, RUNNING HOT

I just had my valves adjusted recently and I took my carburetor apart and cleaned it, reassembled it and fired it up.  The head pipe was glowing orange during the warmup.  Does this mean it is running too lean and does this mean that the pilot screw needs an adjustment? I have it set at 2 1/2 turns.

It might mean nothing at all.  If you run the bike in low light, something like the inside of a normally lit garage after dark, a titanium head pipe will glow red within 45 seconds.  It takes 750-800 degrees to do that, and the normal exhaust temperature is usually somewhere between 1200-1500 degrees.  The header is only about .040" thick, so it doesn't take long.  If the bike moves, the air running over the pipe usually hides the glow. 

 

But an excessively hot pipe could mean too lean, or at idle, it could mean too rich also. Too much fuel, so it burns in the pipe.  Ignore the header and adjust the pilot screw by the book, then set the idle speed, then see what you have.  

 

http://api.viglink.com/api/click?format=go&jsonp=vglnk_14449201892039&key=fd4d0c8927dbf2331e83bbda32ac7c21&libId=ifsc5o1m010004is000DA7nkic4pi&loc=http%3A%2F%2Fwww.thumpertalk.com%2Ftopic%2F378677-common-threads-look-here-1st-mods-maintenance-common-issues-and-faqs%2F&v=1&out=http%3A%2F%2Fwww.thumperfaq.com%2Fjetting.htm%23PJ&ref=http%3A%2F%2Fwww.thumpertalk.com%2Fforum%2F13-yz-400426450%2F&title=Common%20Threads%3A%20Look%20here%201st!%20Mods%2C%20Maintenance%2C%20Common%20Issues%20and%20FAQ%27s%20-%20YZ%20400%2F426%2F450%20-%20ThumperTalk&txt=http%3A%2F%2Fwww.thumperfa...%2Fjetting.htm%23PJ

Thanks for the reply, will do on the settings by the book.

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