Had some fun beaking in a new O.S. 70 Surpass with a 13 x 8 prop a week ago. I clamped my test stand to a saw-horse and set it out in my driveway on a dusting if fresh snow. When I opened it up full it pulled the saw-horse and all a foot or so before I could throttle back! Never tried one on snow before. I was quite impressed.

Manual said to open it up full throttle, but alternate from overly rich for 10 seconds to "near maximum r.p.m." for 5 seconds. After 15 minutes of this 15 second cycle I got pretty good at judging by sound and sight (cloud of oil) whether the engine was running rich or not. I confess that by the second tankful I was letting it go more than 5 or 10 seconds between adjustments, but I was also changing the throttle settings. I think I'm gonna like 4-cycles.

By the end of the second tankful it would idle down and purr like a kitten.