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Discussion Starter #1
1971 cb350 (stock)
Hello all.
I am having an odd issue with one of my carbs, using this video as a reference.
A motorcycle nut: cb350 carb tuning
I set the mix 1 turn out, then warm up the bike (it does this if its warm or not). When I adjust the mixture screw, the idle decreases steadily as I screw the the mixture screw out, and it increases steadily as I screw it in.
It just occurred to me to clarify, I am not turning the idle screw, I am turning the brass mixture screw, i know how that last sentence sounded, and I would have thought the same thing.
The other carb does exactly what the video demonstrated. The idle has a peak (around 3/4 turns) and dives off about half a turn in either direction, so it is a good reference as to how it should work.
My understanding of the cb350 mixture screw is that (because it is on the engine side of the carb) it adjusts fuel being added to the air flow. As opposed to if the mixture screw is on the filter side of the carb like my 79 cb750, it is controlling the amount of air added to the idle mixture. If anyone can give a definitive yes or no to this, I would appreciate it.
Because I have this idea in my head, I am assuming that the carb I am having trouble with is getting too much fuel while idling. This seems to hold true further, because if I screw in the idle speed screw (allowing more air into the mixture) the idle matches up with the wide that is adjusting properly.

I have sprayed carb cleaner around the carb to se if its leaking as well, and it is tight as a drum

I am just about to pull it off again and give it another cleaning. If my theory about too much fuel is sound though, I really can't imagine there is any blockages causing MORE fuel to get into the mix.
For the sake of reference, I got the bike and the carbs were basically solid with 40 year old, undrained gas. They were cleaned, ultrasoniced, cleaned again, and had all new seals and jets installed.

Any thoughts or advice would be so very welcome.
 
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