I have a Brison 2.4 that started acting the same way, I played with it for 2 years, even got so mad one day I kicked it and broke my big toe. I sent it to Brison and he gave me some mumbo jumbo about mixing my gas at 50:1 instead of 100:1. I got it back and it was no better. In desperation I sent the whole thing to C & H ignition. They said it had a weak coil and replaced the ignition system. They also told me that no one in their right mind should ever install a pick up with the clearance Brison has between the magnet & pick up and the weak coil aggravated it severely, they installed a pick up with 1/2 the clearance. After 3 years and countless $'s it finally runs like it should.