Place the piston rings just inside the bore of the cylinder, and notice how much space there is between the ends of the rings, then push them up the cylinder to within 1" of the top and again examine the joint. If the joint is much wider at the top than at the bottom, it shows that the cylinder has worn considerably larger and may want re-boring. If the ring shows a gap open 1/16" when fitted into the mouth of the cylinder the ring has worn and requires renewing. New rings should have a gap of .010". Rings supplied by us are correctly gapped but may need filing to fit over ring pegs.
It is important to note position of piston when removing, as if it is replaced in the reverse direction with the long curve on the top of the piston at the rear, the engine will not develop any power.
Replace head with sparking plug at the front.
Always see, after decarbonising, that all joints are carefully made and that there are no air leaks.