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How to tell if my bike is running lean?

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i have an 06 crf250r and i am just wondering how can you tell if the bike is running lean or if it is running rich? and unscrewing the fuel screw a little will make it run richer right?

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The first tell tale sign is that it will pop on decellaration if it is lean and yes richen it up by going out on the fuel screw:ride:

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I assume by going out on the fuel screw you mean counter clockwise? I started getting the popping on deceleration some here recently and I may adjust mine a hair or two.

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Pull the spark plug. If the porcelien surrounding the electrode is a very 'clean' white, then it is running lean. It should be a tannish color, bordering on dark brown (sooty black means too rich). Also, if your header pipe is a very deep deep purple, you could be lean (purple is normal...dark purple is too hot). I have seen some thumpers with header pipes glowing red they were so hot. Definitely too lean!!

Don't just start cranking on the fuel-mixture screw without knowing how your bike is running. You can make it too rich, in which case youll fould your plugs so badly that it won't start at all.

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agreed, but go to the bike forum and do a search for jetting and see where you should be for your location (ie elevation) and cross that with what jetting your bike has now and see where your at, alot of good jetting help that can get your really close and then you just fine tune

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