readjust idle when warm. If the idle does not drop back to normal after riding and can be lowered by easing out the clutch with the front wheel locked it can be the mechanical spark advance sticking.

Bob

readjust idle when warm. If the idle does not drop back to normal after riding and can be lowered by easing out the clutch with the front wheel locked it can be the mechanical spark advance sticking.

Bob

Agreed. The viscosity of the cold engine oil slows the RPM of the engine considerably. You really don't want to set the idle mixture OR idle speed until the engine is fully warmed up... which may take up to 10 miles or more depending on ambient temperatures, oil viscosity, volume of engine oil, and other variables.

As a long time professional motorcycle mechanic, this has been one of the biggest adjustments for me. Most motorcycles can be set fairly accurately after 2 minutes of run time, but not the Airhead. They need to be ridden quite a long way before effective carb adjustments can be made.

Hope this helps !

thanks for the help this my first beemer

Adjusting the idle speed at elevated temps will easily bring the idle speed down. It should be easy to get the idling in the 1000 RPM range after this change.

However, if you still can't get an even beat you may have additional issues.
• The first thing on any Airhead at the first sign of quirky behavior is to adjust the valves.

• Then, there are several "rubber" carb parts that the ethanol fuel tends to destroy over time. This hardening and cracking is accelerated by some fuel treatments. So it's not IF, but rather WHEN these parts will need replacement. You'd do well to go ahead and get these parts on order and have them on hand as cheap insurance...
- Rubber carb-to-head intake hoses (2)
- Rubber-tipped float needles (2)
- Carb diaphragms (2)
- Various size o-rings on the screw-in jets
- Rubber balance tube connecting the 2 carbs (It is often only the ends of the tube that harden, so usually one can simply cut 10mm off the each end of the hose and re-insert the softer section onto the carb.)

If you brought this bike to my shop and said the words "I just bought it", then I'd be replacing these parts, or at least giving them a very serious inspection as part of your first tune-up or inspection.

Hope this helps.

I got a new to me bike and had this problem. Adjust not just the idle speed, but the idle mixture when warm. Also make sure there is a little freeplay in the throttle and choke cables to the carbs (otherwise when the engine warms up, the expansion from the heat can be like pulling on the cables.)

On mine, the idle mix was way off and there was no freeplay in the carbs so not 100% sure which was causing the problem but adjusting both fixed it. (I also checked and didn't have any air leaks in the intake tubes.)

After all of this, sometimes we see that the idle speed was intentionally set high becasue the idle mixture screw is no longer working. This is a constant and persistent problem for motors with carburetors since the introduction of ethanol laden fuel. And the smaller the engine, the smaller the jets in the carbs, so the more persistent the problem becomes.

So everything I'm about to tell you for your Airhead goes doubly for your leaf blower and lawn mower....

• Smaller jets have a much greater propensity to clog.
• The smallest jet in any carburetor is the idle jet.

So if you see (actually hear) that adjustments to the Idle Mixture screw are having no effect on the quality of low speed idle, or that the motor simply quits running when idle speed is approached, then the idle mixture jet is most probably closed off with gunk created by ethanol fuel. Then the best thing to do is replace the idle speed jet. This is becasue digging around with a sewing needle inside one of these brass jets, trying to manually clear the opening, will enlarge the orifice. The effect of this enlargement will be the inability to restore an idle with an even "beat" necessary for a twin cyl machine.

Now if you want to poke a guitar string or sewing needle though a jet to see if that helps, then you can obviously use this ploy as a stop-gap measure until replacement jets can be obtained, then that's fine. But don't expect 100% perfect idle either.

Jet clogging due to ethanol fuels is why I preach the total draining of ALL fuels before any length storage period for all engines with carburetor(s).

Hope this helps.