Weird Idle Issue

[Solomoriah]

Got my '80 Special sorted last year, fixed the clutch, overall pretty happy with it. But. The idle varies, for no apparent reason. Sometimes when I stop at a stop sign it tries to die and I have to roll a little throttle on to keep it running (or it does die and I sit there looking like an idiot). Sometimes it idles perfect, somewhere between 1K and 1.5K (bouncy needle, best I can do is estimate). Anyone have a suggestion where to look to sort this?

 

[Bruno_c]

First I would try to determine which cylinder is faulty or both. Set idle around 2000 RPM then cut ignition on one cylinder and see if you get a regular tickover. Then change side.

 

[Solomoriah]

Hmm. Wouldn't it run rough?

 

[bosco659]

I would be looking for vacuum leaks around the carb mounts as a first step.

 

[Calliway]

Sounds to me like the butterfly shaft seals in the carbs are leaking. Air gets passed them and the idle is hard to set and maintain.

 

[Solomoriah]

Ack. Trying to avoid taking the carbs apart, but I might have to do it.

 

[gggGary]

In gear or neutral?
Yeah throttle shaft seals PITA AND a must do.

 

[Wingedwheel]

Yeah throttle shaft seals PITA AND a must do.

Usually only the first time. lol IIRC I read that OldSkool Carbs mentioned that a 3mm oring works. Can anyone confirm that?

 

[gggGary]

Usually only the first time. lol IIRC I read that OldSkool Carbs mentioned that a 3mm oring works. Can anyone confirm that?

NOOOOO!
Only the correct seals, and yes I tried a substitute (once)
https://www.xs650.com/threads/the-g...es-used-on-the-xs650-thread.51957/post-547592

 

[Solomoriah]

In or out of gear. I usually drop to neutral if I'm stopping at a light, and usually don't at a stop sign, and it doesn't seem to matter.

 

[5twins]

Yes the seals are so cheap from Suzuki that it's foolish not to replace them. I order them by the dozen, lol.