BK Mod, how do I do it

Hi,I'm new to the list and am wondering if this mod will work on YZF400's, and if it does, how do you do it.

Thanks and I look forward to conversing with you all, speedharris

I don't believe the 400's came with a tab cast into the body of that particular FCR carb where you can drill and mount the BK screw. As Yamaha fine tuned the 4-stroke, they must have worked closely with Keihin trying to make the carb more tunable. My theory is that this tab was added for the benefit of the factory race mechanics and not for the general public. Who really knows?

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