What is "chuggs"? Maybe a video of it?
If it cranks when you hook up the battery, and your not trying to start it, then either the starter solenoid is stuck, or the wiring is not correct. Don't waste time gapping the points, set the timing. For the life of me, other than to get you to a close starting point, I don't know why Kohler even suggests a gap in the book. The gap on a Kohler is used to set time. This engine is not concerned with dwell.
You say you don't have a gauge..... I assume you mean a compression gauge? It really doesn't matter, as this engine has a compression release, and it would give you a false reading anyway.
I'm not sure why you are wanting to replace the regulator.
Please to save you money, test parts and see what is bad instead of just buying and guessing.
Yes, the 020 stamped in the piston means it has been bored .020" oversize. I have no reason to assume that it is an internal engine problem at this point. The simple fact it has been rebuilt doesn't really mean anything is wrong internally.
Did you adjust the valves?
Until I understand what "chuggs" means, I cannot offer any advise, other than on the starting problems. Either a vid, or a better explanation is in order please.
