Took flywheel off....now wont start

On my ryobi 31cc I took the flywheel off to access the stronger mounting holes on the engine. When I put it back on it wont start now. I also took off the cylinder and cleaned it.

I made sure the gap was right and it has spark, I also made sure that everything is there and is working properly.

It just wont start, I think I got it to fire but just wont run.

Any advice would help.

Did you check the flywheel sheer key? I'm not sure about a ryobi but on most engines there is a key that aligns the flywheel and crank to make fire at the proper time. A sheered key would give you spark but not crank as the spark is not in time with the piston. I hope this helps. Good luck.