Here's an update on this thread :
Checked air filter, very clean.
Checked spark plug: Not much on it, grayish-white film only. A friend says that shows it is running 'lean'
I replaced fuel filter. As soon as I did this - immediate change in this way: When it starts up, after a few moments the idle suddenly 'revs' up. Rear wheel spinning. Bike runs okay, and after a moment or 2 driving , no more fast idle..
After a few days, the rev-up characteristic was seeming to normalize.
One day, engine would not start, period. Getting electric, it wanted to turn, but no ignition.
I pull fuel filter to check gas flow.
Confirm gas flow..
Mechanic friend suggests : a valve in carburetor sometime gets stuck open or closed if carb is dirty. Try tapping the carb from outside to release the stuck valve.
Engine fires, problem goes away, though now the rev-up idle characteristic is back.
I'm delaying taking the carb apart to clean, I'm not experienced as a mechanic.
Any suggestions where I can get good instruction on how to pull the carb?
Do I need a "kit", new gaskets, etc?
thanks ahead ~