Things that I have done so far:
• rebuild carbs (enrichener properly assembled and butterfly valve installed in the proper position)
• valve adjustment (triple checked!)
• new points and condenser, and timed!
My last step is to adjust my carburetors. I have read Snowbum's article on carb sync but my idle is way too fast. My idle stop screw is not engaged at all. My butterflies are shut. When I adjust my idle mixture screw to fastest RPM, bike will idle to 2000rpm.
In the video I have linked, you will see the bike idling at around 1200rpm because my enrichener doesn't bottom out. I manually push the lever down and you see my idle rise to 2000rpm. I adjusted my carbs with the choke FULLY off.
I don't know what else to do. I have read Duane's and Snowbum's articles on how to fix fast idle but I don't know what I am missing.
A year and model would help a LOT.
Unexpected fast idle can be caused by...
• No slack in the throttle cables
• Auto advance unit needs lubrication
• Auto advance unit needs new springs
• Auto advance unit re-installed incorrectly after working on points
Owning an old Airhead is easy.
Keeping an old Airhead running great is the true test.
oops sorry. i forgot. r90/6 1975.
i have brand new springs installed and lubricated.
i have slack in my throttle cables.
You ought to have a second look at your static timing. Wobbly correctly advised about a sticking advance assembly or weakened return springs. The reason that these issues can result in a high idle is because ignition timing is slightly advanced when they are in play in the system when the motor is at idle. Another possible factor would be the point gap being slightly too narrow. If your motor still has points, a slightly narrow gap creates its own advance effect. If the gap is not adjusted to spec when the plastic rider block on the point arm is on top of the lobe, the lobe will kick the points open several degrees of rotation too early every time it comes around in the 360 degrees of travel in each revolution.
Another possibility would be a vacuum leak between the carburetor and the intake port of the cylinder head.
former Airmarshal, IL.
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