The nature of the ABC engines is for a super tight fit, especially when cold, at the top of the stroke; the seal is formed by the top of the cylinder being slightly tapered. If you can't get it to start with a stick after 10 or so flips, use an electric starter. THe engine will build up enough heat so that the material will slightly expand, and starting it a second/third time etc. will be much easier.

I don't like the idea of using a torch/heat gun on an engine. Some hobby store proprietor just tried to sell me two engines that he said he had to do this to. They are built to be snug for a reason. If there is any premature movement of the material (expanding) not due to its own break-in process, you will start to lose compression and power.

Again, they are designed to be REALLY snug at the top of the cycle, and will break-in eventually.