Another small idle problem - any help? Options

[StarBear]

Lots of idle problem threads in the Garage, but I think this is a new one not previously covered:
1. 1974 1.8 L-Jet; regular points/condenser and dual port vaccuum cannister.
2. Runs flawlessly and reliably; idles about 1000 rpm at startup
3. Just recently, when at a stop, the idle drops back to only 1200 rpm instead of 1000.
4. If I engage the clutch just a tad the idle goes back down to 1000 and stays there (until the next stop). (IMG:style_emoticons/default/wacko.gif)
I've checked the throttle spring and such. Maybe something with the vaccuum canister or some other little demon hiding somewhere?
In advance, thanks for your knowledge and insights!