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My bike idles just fine, when warmed up, at 1000-1100rpm until I go for a ride. After blasting around for a while it idles at 1500-1600rpm.
Could this be bagged advance springs or sticky weights that are only affected when the unit is heated up through and through?
I can't seem to find any air leaks anywhere - the rubber spigots holding the carbs to the head are new and the clamps are tight.
The advance springs in the bean can are original (120,000km).
It's a head-scratcher. Any ideas???

This is also how my R75/5 has always behaved. Cold, the idle is a bit too slow. Hot, it is a bit too fast. Maybe 300 RPM difference.

Getting a high idle????

A: Does your bike smoke?

B: What does your bike smoke?
















I would reset your idle after you come back from the ride. It might be a bit low till fully warmed up. If your idle is just a tich high, say 1200, you are getting into the begining of the advance zone and the idle will just creep on up.

When set to 1000 when realy hot it will still be below advance and will idle at 7 or 800 when sorta warm.

Can you force the idle back down to a "normal" level by using the clutch to drag the engine speed down and when back in neutral, the idle speed remains at the lower level? If yes, then you probably need to service the advance unit.

If not, then how did you synch the carbs last time? If the engine and carbs are not warmed up over a 15-20 minute ride, any adjustments on the carb won't be correct for a completely warmed up bike like you're describing.

Kurt in S.A.

Another sticky advance test is to......
When the idle is high, turn the ignition off and on as quick as you can. If
the idle drops down, you may have weak advance springs and/or a sticky advance mechanism.

Kurt - I will try that dragging the idle down.
Will probably replace the advance springs anyway - can't hurt.
I think I had the bike sufficiently warmed up when I last set the idle.

It takes a 15 -20 minute ride to warm the engine to operating temp.

I've found that, even with the omega ignition, the bike will do what you described when I have set the idle and it wasn't warmed up enough. Sometimes it takes a good romp around the city to get the bike to full temp. If I do that and set the idle to 1000rpm it's purrrrfect. (sorry I couldn't help myself)

dwerbil wrote:Another sticky advance test is to......
When the idle is high, turn the ignition off and on as quick as you can. If
the idle drops down, you may have weak advance springs and/or a sticky advance mechanism.

That is close to the correct way. When you cut the ignition, wait until the engines slows down to around a few hundred rpm and then switch it back on. If the idle stays down, then replace the springs.

If it climbs back up to the previous too high rpm, then you may be able to properly adjust the carbs, but only after it is quite hot. As mentioned, you could have an intake leak.

Under no situation do you need to drag the rpm down by slipping the clutch. Unless your clutch friction plate is too thick and new. You can help wear out your plate and get it down to a common level of wear by this method.

If I stop with it idling at 1500 or so, go into a shop for 5 to 10 minutes, then it idles fine upon startup.
As for airleaks - I have tried the unlit propane torch trick without any effect.