Hey folks,
I have a R75/5 that is in good tune, starts and runs great, except for a stutter at around 70mph. In 4th gear as I'm gradually accelerating as the bike gets to about 4200 rmp and 70ish mph it stutters a bit, then gets past it and keeps on accelerating. Same thing will happen at slower speeds if I wack the throttle open suddenly.
Where should I look next? Carbs have been cleaned, valves set, points and timing set, new plugs, and new plug wires.

Thanks for some help.