It's working for me.

Success!
 

Finally got er done. Not all that difficult to install.

The only problem was the clearance of the a/p allen head screw & header. Easily fixed with a small ball peen hammer.

The OEM Keihin cable mount bracket wouldn't fit because of the frames head stay crossmember. FSW supplied a new cable mount that went on with out hassel and lined it all up. The throttle pull was reduced to less than 90 degrees making it easier to go WFO. The stock throttle was used with only the pull cable. Jerry included an easily accessable fuel mixture screw to dial it all in on the fly.

Jetting was upped from a supplied 50 pilot & 150 main to a 52 & 152, so I had to install the carb twice. Once to test it, second time to rejet. Jerry said he trial fitted the carb on a klx250 he has in his shop, it made it really easy to get it jetted in. Fuel mixture screw is 1.25 - 1.5 turns out. Didn't even have to do the 'Taffey Mod' as it didn't hesitate at all. Awesome.

The improvement in throttle response was immediately noticeable. The motor revved aggressively instead of lagging like the stock carb. Low to mid range performance was improved by at least 25- 30 % over a DJ kitted 34 CVK carb.

Even on a 250cc motor this carb works excellently. FSW supplied extra pilot/main jets (4 pilots, 4 mains) to get it working properly. Nobrakes & Brewster and others aren't lying, this carb makes the bike a different machine.

Time to save aluminum cans for that big bore kit!

Bumping this very old thread to avoid starting yet another FCR thread. This is a repost of my inquiry on Planetklx, where Brewster redirected me here. I am only interested in KLX 250 jetting, and specifically needle type, as others have covered the 300 and up class fairly extensively.
KLX250 FCR35 jetting tips/ help


Hello, I recently picked up a used FCR 35 on ebay for quite a nice price. I have heard they do very well on both the 250 and 300 as well as the big bore kits. I have the FCR 39 mx on my DR650 and really really like the extra acceleration and overall power benefits.
After searching the web for many hours I am at somewhat of a loss on where to start with jetting. Most people seem to do the carb swap with their 300's or a FCR 37 because of availability, so I am looking for specific info for the KLX 250. Mine is the 1994 model, before the possible CDI retuning and such, and it runs like a son of a gun currently.
My assumed baseline starting point is:
150 main
50 pilot
200 air
slow air needle 1 turn out (this one is a pure guess, as I've never had an adjustable slow air jet)
Needle: Not really sure which needle to go with. I have an EMN needle off of the mx 39 and the stock OCEMR that came with the 35. Once again, I don't know the distinctions between the needles very well.

Any input would be greatly appreciated!

The fcr35 I had was used off ebay so I shipped it off to four stroke works the same guy who built a mid bore klx for team green Larry Roesselar I spelt that wrong I'm sure, give them a call it can't hurt