High Idle

[saintell]

Hullo,it is good to get new ideas on new problems,I have just started riding this bike 84 r65LS and have found I have a high idle problem,which may go away or not,when coming to a stop the high idle will be there if I partially  let out the clutch it will then idle but come back again at the next set of lights,high idle about 3000RPM,when I get home still high idle but feel the exhaust and the right seems not as good as the left,reading other posts sounds maybe like a bean can problem?maybe or carb diaphragms?I also notice at hiway speeds 60mph it seems to be a bit fluttery with hunting problems and not happy at all,but will pull good with more throttle,looking for suggestions,cheers Nev from OZ

[Session101]

sounds like your advance mechanism is sticking...

[Barry]

Idle speed hang up can be carb settings or sticky advance mechanism.

What is your fully warmed up idle speed - once it's settled down that is.

BMW specified an idle speed of 950 RPM  + or - 150  If your idle speed is higher than this specification then there will be a risk of idle hang up.

[nhmaf]

Before you dig into the bean can/ignition timing sensor, it is best to be certain that your valve adjustments are correct and the carbs and throttles cables are at least pretty close to adjustment and in synch without air leaks.   These things can have a major effect on idle, too.    If you know that these things are properly set and you do still have the issue you describe, it does indeed sound like sticking advance mechanism in the bean can.

I set my idle speed on the R65 at between 1000 - 1100 rpm.   The older, larger, heavy flywheel bikes can idle just under 1000 rpm smoothly, but I find the smaller R65 and the light flywheel/clutch bikes are much smoother idling a little faster.

[saintell]

Hi all,thanks for the replies,I did have the idle speed at 500,warm, but I will boost it up a bit,it ticks over like a swiss watch,cheers Nev

[montmil]

One issue relating to a below specification idle on the Airhead is the issue of oil delivery to the timing chain and front crankshaft bearing. A low idle results in little to no oil reaching this critical parts. Not good, that.

If you've ever replaced a timing chain, you may have noticed the rather Stone Age bent pipe that is supposed to spit out oil for a semi-splash lubrication system of the chain and ball bearing.

Low idle reduces oil pressure and effectively shortens the "spit distance" to the bearing. These classic Airheads will take abuse and keep plugging along but running dry bearings is never a good idea.

[nhmaf]

Yes +1 with Monte - 500 rpm is definitely too slow for these airheads and you're not getting enough lubrication at that slow a tick over

[Barry]

The effect on idle speed on timing chain lube is a good point and worth expanding on.

The real limitation on oil coming out that bent pipe is oil pressure as it is simply the outlet from the pressure relief valve which is set at 70 PSI (I'll check the exact figure when I get home) and the oil pressure at idle speeds will vary so there is not necessarily one set minimum idle speed to guarantee adequate lubrication. It will depend on operating conditions.

For example I don't think there is a need to worry about low idle speed when the oil is cold as the relief valve should be flowing at vastly lower RPM than normal.    

When the oil is at working temperature you should be more worried if you are in a hot climate or if you opt to use thinner grades of oil or your engine is worn or if the engine runs particularly hot for any reason as it will impact on oil pressure.

All that suggests that those in cooler climes may be able to opt for a slightly slower idle speed if they wish but when the going gets hot it may be best to keep the revs up a little.

[Ed Miller]

If you guys have to worry about that stuff, you spend too much time with the bike idling anyway.  Hmph.