this is what someone told me in a simular post i made:

Ahhhh, this is an age old subject that has no right answer, unless the answer is yours! How long to break in an engine???

I think that for an aircraft engine, 3 tanks of fuel should be fine. That is my (very general) rule of thumb and has worked on several engines. A good indication is (after you lean it out over this process) how it accelerates. Can you go from idle to WOT without hickups? Is it smooth during the transition? How does it start? Is it making full power? If it does not seem ready after looking into these things, you might need to run another tank through. Also, a bad mixture will give bad indications such as these, so make sure it is right on!

As for a high performance NovaRossi type race engine for cars and trucks, you will need more time (like 6 tanks) to break it in due to a tighter fit of the piston and sleeve. This is what I did with mine, and now it still screams with over 1 gallon through it. It is moving my RC10 GT, so it has its work cut out for it!

Good luck!