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Keihin FCR?

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Hey everybody. Diving into the realm of jetting. My '00 WR400 seems to have the later style FCR according to the fuel screw and main air housing orientation (not level). 5G55 500A06 scribed into the side of the lip on the bowl. Mean anything to anyone? Sould an '00 have this carb? As far as I knew I was the third owner and it came from OR. Has yz timing, grey wire mod, throttle stop cut, e2 header and pipe (larger main jet), unifilter, lid removed and other goodies. Ran great for a while now time to mess with that darn FCR. Started fouling plugs (sooty black) and running bad. Will only start with a few twists and a few to ten tries. NW Washington (~50 degrees, 500-3000ft elev.) Takes a while to idle up to choke rpm's, backfires when cold, hesitant on good blips, idles rough, pops sputter even at half to full throttle (warm). I haven't yanked the carb fully apart. Needle was at 3rd to top clip (OBDR), changed to 2nd since fouling plugs, still runs bad and harder to start. I don't know what main jet is installed (was told correct for e2 and airbox mods. Rest of jets probably stock. Any suggestions? Head pipe and mid pipe joint currently leak (not to bad). Gap is to small for a donut, to big w/out anything so I used header wrap. Worked for a while. Is there a part from White Bros for the head pipe to mid pipe mating? Thanks for your time. Sorry so long!

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Check the pilot jet. It should be a #42 or #45. If you have a #48, switch to #45.

Set the fuel screw further inwards to lean the idle mixture. Your plug fouling is from the pilot circuit or clip position, but the 3rd from top on OBDRS is lean enough and 2nd seems excessively lean. The float bowl level should also be checked along with air passages.


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