This is copied directly from the BME Manual: Page #8

BREAK-IN OIL:
We recommend the use of a petroleum-based oil, such as Lawn Boy Ashless or Stihl Chainsaw oil for breaking-in all BME engines. Use the break-in oil until approximately 5 gallons of fuel has been run through the engine. ALWAYS MIX THE OIL ACCORDING TO THE MANUFACTURERS INSTRUCTIONS!
Using the break-in oil will help to ensure the proper seating of the rings to the cylinder walls. This is IMPORTANT if the full potential of the engine is to be realized.

Every other engine manufacturer calls for 5 gallons as break in time BME is no different.