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won't stay idling

lukers

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warren, maine
I need a bit of advice. I have a 78 cb750f (supersport). I recently rebuilt my carbs, and now the bike won't idle. I'm not sure where to look first. I have the air mixture screws backed out 1.5 turns. The idle screw adjustment stop doesn't seem to do anything.
Thoughts?
 
The 'stop' as you call it does nothing, it's just a stop.

Are you saying it idled before? Your use of english seems to say so.

' idle screw adjustment'

What do you mean by that??? There is mixture and speed, you have to know which one you are talking about.

If the carbs were not resynced to each other after the work to all open exactly the same you'll have fits there. It would seem you are already there.......................
 
I synched the carbs while off of the bike. I used a very fine piece of wire to adjust all the slides the same. The 'idle stop screw' was the ,for lack of a better word, knob that stops the throttle from returning all the way. I assume that would keep it idling, so I called it an idle adjustment. The air mixture screw on the bottom of the carbs is what I have turned out 1.75 turns. I have not replaced the slow jets, or cleaned them, and I think I'm going to start there.
 
If the bike runs kind of okay, just won't idle, I'd run a tank with sea foam before taking carbs apart to clean or replace jets. Easy p0easy and you could get lucky.
 
By the way... I was cleaning the garage today and came across a Carbtune I used a couple of times, once on a CB900C and once on an SOHC 750. I have no use for it anymore and will let it go for $80 shipped to the lower 48. If interested I'll get it rounded up and provide pictures.
 
'I recently rebuilt my carbs, and now the bike won't idle.'

Strongly suggests something wrong that wasn't before, it screams look the work done over again.

If the slow jets are the usual 35 or 38 you can use an 'E' guitar string to clean them out, the smallest wire they use. Around .013" or so, the size of the hole in the jet. Need to pull them as well to guarantee the air bleeds that run sideways above the metering hole are clean too.

If you have simply gotten lost in the idle speed screw range the bike will not idle until the speed screw cracks the slides open enough.
 
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