"Have been doing a bit on my 84 Kr250 and having a bit of trouble getting it fired up. I have good compressions, clean carbs and fuel, spark when I kick it over. The spark is good at kicking speed, but when I put it on the rollers and give it a spin the plugs spark twice and then stop. Seems that when engine speed gets above kicking speed something stops working. Any clues as to what might be the problem?"
All opinions greatly appreciated, thanks.

Paul