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Discussion Starter #1
When its pretty hot out and I'm in stop in stop and go traffic my 2000 CBR f4 starts to 'stumble' when idling. For instance, when stopped at a light and the bike engine temp gets fairly high the tach needle start to drop down to like 500rpm then back up to 1200rpm where it usually idles. Then once I start to go the engine stumbles and makes the first 2-3,000rpms jerky. But once I;m up to speed everything is fine. Any ideas??
 

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second chimp in space
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3,344 Posts
Um, no. Your bike is running too rich. If it gets worse as the bike warms up, it's too rich (think why you have to use choke on a cold engine, to richen it. You turn choke off once it warms up). From the sound of it, only the idle mixture is too rich. This is adjusted by a screw, so it's relativly painless. Some bikes have a plug to keep you from messing with the screw that you have to drill out, but I'm not sure if Honda did that or not. Once you get at it, turn the screw in 1/2 - 1 turn on each carb to lean it out at idle.

Can you idle the bike for a while, then kill it and look at the plugs? What color are they?

When it idles and you blip the throttle, what happens? If it stays high for a while then drops down to idle speed, it's lean (or an air leak). If it drops below idle then climbs back up, it's too rich.
 
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