This turned out to be a combination of 3 problems, i tried stalling the revs down from the 2500 by slipping the clutch with the front brake on...hoping to test the advance this made no change as soon as the clutch was pulled the revs went back up.
Next i changed the rubbers to the head (see photo) as you can see they were in a bad way this brought the revs down to about 1500.
Next i stripped the carbs and found two issues firstly the butterfly on the left hand side was sticking open about 1 mm secondly the enricher on the right hand carb wasnt shutting off properly, this bike being the 81 has the "choke " on the handle bars and a splitter under the tank, the 79 (mine) has the enricher mounted on the clam shell and 2 direct cables. There are return springs on the 81 but there not that effective.
ran it up revving at 850 ish so a balance and tweak set tick over at 1000 took it for a spin ...spot on.
Lou
