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Does anyone know where I can get the right float seat replacement for my keihin fcr mx 39? 

(Not sure if it makes a difference but: 03 yz450f)

Mine was leeking so I pulled it out thinking the Oring was bad but it didn't have one. I've looked up replacements but mine doesn't look the same.


It's a press fit. Had a inner diameter of about 0.254 inch on the seat. The whole at the bottom is about 0.145 inch. The outside diameter is about 0.388 inch. The groove on the outside is 0.323 inch. It's got 2 wholes in the groove drilled 180 degrees apart from each other.

(Sorry, I don't have a metric dial caliper)

Ignore the threads. They are from my puller.


In case your wondering how I got it out. I made a puller by drilling a whole in a 12 mm socket, tapping the float seat, and threading in a chain tensioner to get it out. Probably not the right way but thats what I had to work with.



This a terrible picture of where the float seat goes.

I would appreciate some pro tips before I order the wrong part. Thanks!

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  • 1 month later...

Yeah, I replaced the whole carburetor. On ebay you can get one for about $130 and it works great.

I contacted keihin and Sudco (a supplier for Keihin), and they said that part isn't ment to be replaced. It would be nice if they looked in the factory to see if they had any laying around, but they wouldn't make any money if they let us fix everything.

If you find someone who makes the exact part for my carb I'd love to know, but so for I haven't found any that fit, and I'm not willing to gamble $20-$60 on a part that may fit.

I'll probably end up re-machining the part myself one of these days, just so I have a spare carb.

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