I don't know how outdated this info is, but it's worked for me before on a couple two-stroke bike engines, a Z50, a Ford 8N tractor and a AMC six in my old Jeep...on the first break-in oil, you want to get the motor up to temp fairly gently, then run it through the gears until you're in high gear and do a couple of full-throttle roll-ons from a low-mid rpm up to a mid-high rpm...not starting low enough for it to be lugging, but so it can snort a bit, and letting off before it really revs out. Then decelerate with throttle closed back to your starting speed each time. This loads the rings against the cylinder walls with compression and then deceleration vacuum. Repeat several times.
Also, during that break-in period, don't hang at one steady rpm for too long; vary it as much as you can stand to. This is sort of funny to try; it's harder than you might think.