Terry is right on with keeping the one you have unless you have money burning a hole in your pocket that OX 66 will run like the energizer bunny. I even know a guy that ran his out of oil, locked it up, and then got home and freed it with a breaker bar. Still running from last I hear.
If you do come over to the dark side and go with the 4 stoke, don't listen to the every 100 hour nonsense. The motors are no different than the car in your driveway.... Change the oil every 100 hours and forget them. I have one with 10 years of hard azz, offshore running and am approaching 1800 hours. No valve adjustments, fuel injector cleaning, or any other "recommended" BS. The BRP gang would like you to think different but they're just jealous cause they can't run the cheap gas.