Well seeing rajul asked about precautions..

You can get a hydraulic lock if the cylinder lays over past horizontal. Excess fuel then fills the combustion chamber because it can't run out the exhaust port. Hit it with the starter and something's going to give. Either the starter slips on the spinner or the weakest link in the engine will give. That's usually the con rod and it either bends or breaks. A bent rod is easy to diagnose because the engine will get tight to turn even with the plug removed. So with an inverted engine ALWAYS turn the prop over by hand a couple of times before using the starter. If the compression suddenly feels a bit higher than usual then it's on the verge of locking.

If you have a bushed engine then it MUST have the steel thrust washer fitted between the prop driver and the crankcase. This is the only thing stopping alloy to alloy contact from the pressure of the starter pushing the crankshaft back. It's wise to put a few drops of fuel on it before using the starter to make sure it's got at least some lubrication.

Don't expect fuel to get drawn into the carb just by spinning over with the starter. This is where real damage can be done. The engine must be primed first in whatever your favourite way is. I once watched 2 guys spinning over an engine for a couple of minutes waiting for it to fire up. It didn't so I had a look at it. There was black oil coming out past the prop driver, it was a bushed engine and the crank was almost seized in the bush from lack of fuel. I got it freed up for them but who knows what condition the piston and liner were in?? Do that with a ball raced engine and either the piston or rod will go first.