Topic: 1975 CB550K idling very rich - can't figure it out. HELP!!

[goldarrow]

Did you ever take out the emulsifier tubes for cleaning? That should help clearing up rich condition greatly. 

And yeah stock jets are 38 and 100.  Needle 4th groove from top. 

[reddyvv]

Yup, did all that several times. Turned out that the jets were larger than stock, probably from just being cleaned roughly. I tried measuring and was sure they were original size - bad mistake. 

[Duanob]

I had a rich condition problem that was related to the needles and emulsifier tubes. The needles had some crud built up just where the needle sits in the tubes leaving them hanging a bit enough to let fuel through when it wasn't supposed to be. After completely dismantling the slides and needles and cleaning them thoroughly, no more rich condition, no more hesitation off idle. Maybe a new set of needles and emulsifiers? They do wear over time. They do need to checked, cleaned or replaced. If your tubes have been enlarged, that would cause a rich condition at idle. The needles should shut the fuel off completely when the throttle is closed. If not too much fuel at idle.