Just a quick note, Changing the rings on these particular engines is a pretty simple job for the home, and much more cost effective to do yourself.
Take off the cowls, then the 4 head bolts, pull of the head, then slide off the cylinder.
Remove the piston (careful not to bend anything) and inspect it, then swap the rings over carefully (you can use an old ring, filed to a point to clean the grooves) refit the piston, whack on a new cylinder gasket (after removing all the old one) and compress the rings as you slide on the cylinder.
Slap in a new head gasket, refit head, bolts, cowl, and you are done.
With the timing, I'm having trouble understanding what you are using to reference the timing, the spark needs to be 3mm before TDC (top dead centre)
