[vettestr]

Conman,
As mentioned several thing can cause run-on. High idle speed can cause it so check your RPM and reduce it higher than normal for your engine. 750 to 850 RPM is a ballpark but this depends on what's in your engine. Sticking float levels are another possible but other symptoms would be present. Badly carboned plugs or combustion chambers can cause run-on so maybe your meck a nick who can see and hear it run would be your best bet.

You can stop the engine run-on by holding your brake down and releasing the clutch with a little finesse and her in high gear.