It did this same thing the other day and I changed plugs, gave it a quick squirt of staring fluid, changed fuel supply, but nothing seemed to help - then it just started running right again. Now it's back. Sounds like it's starving for fuel. But I think it's electrical. I also noticed this time that the tach is jumping erratically, like it's grounding out or something. This motor was just rebuilt, including carbs about 50 hours ago. What's up?