Topic: high idle problem

[KeithB]

I am experiencing an idle issue with the '72 where , when it's warmed up, the idle won't come down from about 2200 to 1000 unless I twist the throttle closed.
No problem with the '78K, just the '72K
Valves checked, timing done, carbs synched with vacuum gauges, floats checked,return spring and throttle cables checked,adjustment of throttle cable at carbs for some play checked,idle air mixture adjusted, plugs new.
No leaks at intake boots , new stock exhaust.
Any other suggestions would be appreciated.

[Gordon]

You listed pretty much everything except for adjusting the throttle stop screw between carbs 1 & 2. 

Other than that, check that the ignition advancer unit isn't sticking open. 

[KeithB]

Thanks Gordon

[neil10]

check idle with cables off
also check leads and caps for arcing can cause idling issues

[spdiii]

Maybe this will help. I had the same problem after I performed a tune up. Turned out to be the points gap. I had left the gaps where they were when I got the bike, at the lower end of spec (0.012) and had the same condition you describe. I then set the gaps mid-way at (0.014) Wow, what a difference! Idles perfect and I now have acceleration I didn't know could be attained.

Nick

[KeithB]

I will re-visit the gaps!
Thanks!

[sbc1320]

I am with taking the cables loose and setting the idle, then adjust cables where there is a tad of slack in them. Also if you sync'd the carbs make sure it was done with the motor warmed up or it will be idling high.

[jph550]

There defineately should be some slack in the throttle cable. how much? 1/8" I think. the manual should say.

funny thing on the points gap, I always put it towards the smaller gap. would one be better than the other across the board, or is it more important that they are the same. be sure to recheck your timing after adjusting points as it could change slightly.

[Gordon]

funny thing on the points gap, I always put it towards the smaller gap. would one be better than the other across the board, or is it more important that they are the same.

I always set the points gap in the middle to upper range of measurement, because as the rubbing block wears down over time the gap will decrease.

[KeithB]

It's not that the engine won't idle at the correct RPM but after it's warm, it will idle at about 2000RPM until I give the throttle a "close" twist.
I have to do this at every stop.
Then it will idle OK.
As soon as it has been revved up a bit, same problem.
Only when warmed up after a run on the street.
The idle stop is not set incorrectly and the throttle cable has appropriate slack.
I will let you know after checking the points again.

[spdiii]

Thanks Gordon, I hadn't thought of the rubbing block wearing over time. That makes perfect sense. There is one other thing KeithB can check, Throttle return spring might be worn or stretched. Sometime them B*&%#'s get that way from too many wrestling matches.

Nick