Mustlust,
Check your butterfly disc clamp screws. If they come loose, the butterfly disc can slide around in the spindle and stop the throttle from closing fully. Remove carbie, back the idle screw right off and close the throttle lever. There should be virually no light showing around the disc. If there is, make sure that the spindle nut at the throttle lever is tight, then loosen both disc clamping screws and centralise the disc while holding gentle closing pressure on the throttle lever. Use some loctite on the butterfly screws so they don't loosen again. Be careful with the Loctite, any runoff will lock up your butterfly spindle bushings.
Also check that your distributor centrifugal advance is not sticking, as this will cause high and erratic idling speed. Most advances don't get much attention and need to be checked and lubed every few years. Sometimes the springs get rusty or stretch and allow excessive advance. Turn the rotor against the spring pressure - it should be firm and snap back fully and smoothly with no play in the springs. Also, check your vacuum advance diaphragm for rupture or leakage as this can upset the mixture.
I hope this is of help. Good luck! - 5380
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