heres what one guy said

Mike: You have a great engine. I have two of them, and have learned that the tank placement is critical. The tanks in mine were both low, in relation to the carb, and would run fine @ low end, and mid-range, but would die when I advanced the throttle. I re-located the tanks to approx. 1/8 inch above the carb center, and both engines ran well. Also they require considerable break in time. After this, both engines run at about 10,500 w/a 13X6 prop, and idle at about 1800 rpm. Be patient w/your engine and you will be rewarded w/a long service life.

Good luck, Bill