Keihin Cr Special Carburetor Tuning Manually

Posted By admin  On 24.05.21

CR-SPECIAL STANDARD JETTING SPECS 26mm 105. Honda Kawasaki Keihin CR Special Smoothbore Carburetor Owners Manual. Keihin, CR, Special, Carburetor, Owners.

Keihin carb adjustment

I recently had the pleasure of performing a complete frame down rebuild on a 2007 CRF250R that came to me with an intolerable bog issue when the throttle was stabbed from idle or low RPM (both when riding, and on the stand). After the head was rebuilt, and the engine freshened up with a new piston and rings, the lean bog was still there. There is very little in the Honda service manual regarding the accelerator pump circuit, or leak jet, so I documented the process that I used to solve this problem, and decided to share.

The information presented here is applicable to any brand of motorcycle that uses the ubiquitous Keihin FCR carburetor.

If you are experiencing the dreaded “lean bog” when stabbing the throttle on your Keihin FCR carbureted dirt bike from low RPM’s you don’t need to buy expensive “fixes” such as the Boysen Quick Shot or the R&D Racing Power Bowl… you simply need to tune your carb using the adjustments that are already there… I'm not saying that Boysen or R&D hasn't come up with a valid fix, their products certainly make it much easier to properly adjust the accelerator pump to tune out the bog, my opinion is that in most cases you don't really NEED those items to fix the issue... In the case of this particular bike, it only needed a $10.00 leak jet and the problem was solved.

Keihin Cr Special Carburetor

Please follow along while I present my case :-)

Keihin Carburetor Diagram

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Keihin Carb Adjustment