idle question

Hey guys,
I got my 82 750 Maxim running and starting good with your guys help, but i have a slight problem. On startup and sometimes between gears the RPM's will jump up to about 4 grand. It's not in the throttle cable, plenty of slack, and it's not the carbs itself getting hung up. I hear a nice "ting" when i let go of the throttle, right up against the idle adjusting knob. It's not a strong high idle as when i let the clutch up it drops right down and stays down, it's just very distracting. I went through the carbs very thoroughly and the brass slides are clean and pass the "clunk" test. The problem is random, sometimes it happens every shift for a mile, sometimes it's gone for a half hour. Anyone got any ideas??? Thanks in advance guys.

Chris

 

Usualy after a carb clean it is the result of ill-sync. I would also check and make sure the carb boots are all tight and not leaking. Air getting in due to a vacuum leak will do the same thing.

 

Sadly this is V common. Assuming there are no air leaks you can get some relief (i've found) by judicious adjustment of the Idle screw.

 

Are the clutches new? Or, does the bike have low miles?

 

Let's not forget the possiblity of worn butterfly shaft seals.

 

Good one Nick , maybe its the time factor creeping in at this date/timeframe for those butterfly shaft seals on all original seals.

 

Not entirely convinced that the Butterfly seals are the only cause. Having owned and even Raced a few BMC products..SU's and their perennial prediliction to leaking Shafts.. I double checked mine.. Carefully, even pressure testing.. damned 'Vairable idle' was still a problem.
IF there is a genuine cure, I'd be gratefull.

 

The pressure testing thingy 's got me ?, anyway the 2 outer carbs , still on bike maybe , put gob hole on the place where the seal is and suck or blow , see what happens , then do same at different throttle positions , see what happens , thats only 2 seals if any leaky a bit expect inner ones to be worse.

 

this same thing is happening to me as well. I have another post out there somewhere describing the same problem. I found that when I unplugged my hose coming off carb#2 into the petcock, the problem went away. Do you have that hose on your bike? Then, in a response to my problem, somebody said that could just be too rich of a mixture going in. Have not had a chance to test this because I do not have the right tools.