HI
the engine break in is the single thing that will determine how long and how well the engine will perform through out its lifeexcluding crashing
the engines metals are polished and seated at this time to each other the better the surfaces are polished the smoother the metals the better the engine will be long term ( polishing is accomplished with extra lubrication on the first few tanks of fuel -and cooling completely between runs)
best to get the needle valves set to keep the engine running very slightly richi use the pinch the fuel line method to be sure i am rich top and bottom-mostly applies to glo engines
get the engine into the air A S APso it breaks in under actual flying conditionslimit your bench run time as these engines are air cooled and do require air over there surfaces to prevent any over heating which cause a lean run which must be avoided as much as is possible through the engines life-aluminum is soft and will warp from high heat
staying with one fuel and prop from day one will keep the head temps of an engine always close to the same temp
building flying and rebuilding for 26 yearsMORE THAN MOSTLESS THAN FEW
BEST REGARDS TONY