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Rich or lean CRF450

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Posted by: parkerCR---------------------

How can you tell if your bike is running rich, lean, or just right?
I have an 2004 CRF 450 and am curious if there is a way to diagnose this without pulling the spark plug. I am used to two strokes and can identify this. Anything to help in diagnosing how she is running?

Thanks,

Parker


Posted by: Hick---------------------

Quote:
Originally Posted by parkerCR
How can you tell if your bike is running rich, lean, or just right?
I have an 2004 CRF 450 and am curious if there is a way to diagnose this without pulling the spark plug. I am used to two strokes and can identify this. Anything to help in diagnosing how she is running?

Thanks,

Parker



Well, I wouldn't trust the spark plug anyway due to the presence of an accelerator pump, and you can't tell which carb circuit is doing what anyway.


To eliminate the pump from the equation, hold the throttle steady and keep it in the same gear. Any surging or other abrupt rpm changes usually signify a lean condition. If it is too rich it will stumble when you roll it on slightly.

You can also artificially lean things out on-the-fly by using the hot start, this is especially helpful when trying to sort out the pilot and idle mix. If it runs better as you open the hot start then you may want to try some leaner settings.

Unfortunately the only real way to figure this out is to make a change and then ride the bike. Make sure your bike is totally warmed up before you pay any attention to how it is running and only change one thing at a time. You can change the main and pilot via the drain plug (it is easier if you rotate it slightly, but w/ a small mirror you can see what you are doing w/out having to move anything), and the needle and clip with the tank and seat removed so you can access the top of the carb. You only have to remove the carb if you want to change the accelerator pump diaphragm or air jets...


Hope this helps.



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