Hi Bill
Now that you mention this, I saw this happen yesterday while running a Mac 32cc, I just converted and was testing. The first thing you think of is if you machined the flywheel off center or something. When I increased the RPMs a bit the prop tracked true, but I could still see what you described along with the prop tips reacting to the load and RPm of the engine. I will have to try a different position. I more or less have it lined up with the magnet and counterweight for ease of propping, but maybe that is not the best position.
John