R100 CS High idle when hot

[Rob Frankham]

Regarding sticking advance timing i guess that i shouldn't be possible with electronic ignition.

On your '83 model, the trigger for the ignition is electronic (instead of points) but the advance mechanism remains fully mechanical.
The weights spread with centrifugal force to advance the timing as rpm increases.
It is not uncommon for these weights to erratically stick because of weak springs or grunge build-up.
Don't take anything apart yet, get a timing light and check the timing through the inspection hole near the dipstick;
The marks on the flywheel can vary by year and model; typically you should see a "S" (slow) at idle speed, and F (fast) or Z(zoom?) at over 3000rpm.

Thats just incredible information. i was so convinced that there wasn't any advance mechanism. I will definitely take a look at it this weekend.

A slight rider to that information. There have been fully electronic 'bean cans' made for the airhead as after market bolt ons. Some were made by BMW and had a reputation for being unreliable. Others were made in the 'aftermarket' and there is little reliable information available on reliability. If your bike has been fitted with one of these, all comments about mechanical bobweights are irrelevant although that doesn't mean that the problem isn't in that area.

If a timing lght shows the advance working properly, whether it's mechanical or electronic, then I would be looking elsewhere so, to my mind, that's the first place to go...

Rob