I just got a Keihin FCR carb from an '05 WR250 off of eBay. I got it for a steal ($51.00) because it was used for parts - specifically, somebody took the main and pilot jets out, and the needle is missing, according to the seller. It needs a float valve too. I know this is a 37mm carb, but I'm planning on going with a 340 kit, so it should work for me.

I know Nobrakes and others have played around with 35mm FCR's, and I was wondering what jetting you guys were running? I could get the stock jets for a WR250, but if you guys have already got your carbs close to dialed in, that wouldbe much better to start. They make Dyno Jet kits for the WR250, but I don't want to buy a kitwhenthe carbmight bealready too rich.

Also, has anyone tried one of those Quick Shot accelerator pumps on their FCR? I assume that they are like puttingbigger pumps on a Holley double-pumper. I'm curious if it would increase throttle response even more or cause a big bog on our bike.

Thanks a lot.

 

For the 35mm FCR, I'm currently running:

Pilot: 52
Needle: OCEMN
Clip Position from top: 4th
Main Jet: 152
Fuel Screw: 1.5 out
Main Air: 200
Pilot Air Jet: 1 out

I've run it leaner and it works fine but I noticed some popping on decel. The above jetting seems to be work pretty well. I've not tried the quick shot. Good luck and let us know how it works out!

 

That was exactly what I was looking for! Thanks a bunch Nobrakes! As soon as I get everything together, I'll let you all know how it works.

 

Oh, I should mention, I'm running without the airbox lid for max air input. I still have my backfire screen, though.