Carbon buildup will raise the compression ratio, making it harder to start. I don't have a parts list here at the house, but there may be a thicker gasket available, which will lose a little bit of power, but not much, and make starting easier. Be sure the flywheel key isn't sheared a little.
This is why all the new high RPM engines, from just about any manufacturer, uses a chip in the module to change the ignition timing electronically. It has the timing retarded at starting and idle, and advances it as RPM goes up. Also lowers emissions some, as well as giving more power under load.
I haven't seen any manufacturer make new ignition module technology available for older units, with maybe the exception of some of the CDI trigger kits like STIHL made for the 028, or the B&S Magnetron kit, but all those did was replace points with a solid state trigger, nothing happened regarding timing.
