I have a 1991 MC 21, fairly stock but de-restricted. I have had it for about 4 months. Bike runs fine around town but once on the motorway and being at above 7000 RPM in 6th for over a couple of Km's the bike starts to lose power, like it is running out of gas, after i pull over the bike often stalls. Once it has been kicked over a couple of times it usualy starts and then runs fine at slower speeds, by this stage i am off the motor way so it does not get a chance to do it again.

To get rid of the obvious, yes there is gas and oil in it and the plugs are new.

Any help on this woud be greatly appreciated as it is doing my head in.