I have run about 1 gallon of gas through my MVVS 35. I continually get black slop out of the engine. I talked to Morris Hobbies and they suggested switching to Lawn Boy ashless 32-1 (from HP2 40-1) for break-in. I can't get rid of black goop and can't get engine to 2 cycle in mid throttle range. I have about three clicks of high throttle, then as I back off, the engine four-strokes, Morris suggested running more fuel through on the ground (it's in a WM GS Zero). Additional 1/2 hour of running, and leaning of low screw has resulted in no change in slop or mid-range burble. Any ideas or thoughts out there?