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One other possibility with high idle when warm is sticky advancer weights. When it is idling fast try slipping the clutch in first gear while stopped to bring the idle down to about 750 - then disengage the clutch again. If the idle stays low for a while you have identified the problem. Of course you could also just check with a timing light to see if the timing is advanced at idle - but at 3000 RPM you would see some advance anyway. Just as an aside - I had a similar problem on my R75/6. To make it worse the PO had snapped off the 10mm nut holding the advance unit in place and brased the nose so it would stay on! the Omega electronic ignition unit that mounts on the end of the crankshaft over the generator worked as a replacement.