250FR Keihin FCR Carb Question

Hey everyone.

I pulled my 250 out of storage now that I have recovered from my shoulder surgery. The bike has been running terribly lean from idle to 1/2 throttle. At night I had the exhaust glowing a vibrant shade of red. This morning I took the carb apart and cleaned it top to bottom, with a 15 minute dunk in the ultrasonic cleaner. After I reassembled everything, the bike idled as badly as it did before. The only way I could smooth it out was by turning out the pilot screw at least 3 1/2 turns. I assumed at that point that the circuit was still plugged so I took the carb back off and dissasembled it once again. While blowing compressed air through the pilot circuit, I noticed that a pressed in detent ball in the pilot circuit appears to be missing. I'm wondering if a ball is supposed to be there at all? The starter circuit detent ball is pressed in on the other side, so I can only assume that the pilot circuit should have one too. Would someone take a peek at one of their FCR carbs for me and see what's up? Here is a picture:




Sincerely,
Kellyn  

What year is this?  
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I love this dirt stuff.

I believe it is a 2003 YZ250F.  

Welcome 11 !! Most modern day 4 strokes have a header pipe that glows like lava at night time.  Its normal.  Had u made any fuel screw adjustments prior to removing the carb??  

No, none whatsoever. But from my experience with engines in general I figured she was running lean during idle and extremely light cruise. It was backfiring constantly and was surging. Prior to removing the carb I checked the TPS with a multimeter just to be sure that it was carb related. I'm glad that the glowing was normal; someone at the place I ride said that most modern 4 strokes do that but I wasn't so sure. I build turbo'd cars and rarely do we get glowing manifolds!

Kellyn  

Admins, would you relocate this thread to the tech section? I apologize.  

Well, after some more inspection I found that I was wrong about ball. The circuit in question was not the idle circuit; it's the starter circuit. Furthermore, the circuit has a copper insert which makes the circled hole unimportant. After realizing this, I put the bike back together. Man it ran just as badly as it did before, and I was becoming really frustrated. I chose to open the manual one more time and go over every possible carb problem. Upon inspecting the exploded view of the carb in the manual, I noticed something so miniscule. When I reassembled the carb, I had noticed the embossed "M" on the black slide plate was upsidedown while the carb was rightsideup. I just put it in the back of my mind and forgot about it until I looked at the exploded diagram. It clicked. What an idiot I am. I did fix the carb! I just put the slide plate in backwards! I raced outside to dissasemble the carb and whaddya know, I had the bugger in upsidedown. 10 minutes later and the bike is idling like honda civic. Whew, what a relief.

Note: I am in florida. The bike came with a jet setting of "4" which produced a lean spot under 1/4 throttle cruse. Dropping it down one notch solved that.

My idle enrichment is 2 turns out. It could come out some more but I don't like how loose the screw feels past two turns. Weak spring I suppose.

I hope my thread helps anyone caught in the same rut I was

Sincerely,
Kellyn  

ki11bert:
Admins, would you relocate this thread to the tech section? I apologize.

Welcome, I can move it but no harm where you posted.  I sent alink to one of the editors who may have something to offer on it.  
.
Dave H 2006 YZ250
(2008 YZ 125 son)

Great fix killbert and there are no idiots here and yes your thread helps. Thanks.  
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I love this dirt stuff.

Thanks a lot for this post.  I had my carb off about 15 times, inspecting and cleaning to try to get rid of the decel backfire and surging at low throttle opening.  I had noticed that the wear pattern on the plate didn't make sense but I didn't follow it through.  The plate is shaped similar to the slide and looked to me like it should match up but it was the wrong way.   Bike runs fine now.  I don't know when it would finally have come to me but you saved me some time.  Thanks again.  

killbert says your welcome.  
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I love this dirt stuff.