I should add that I blew a 7 session old ISC motor this spring, and in about 2 laps! My Yaw carb never returned from a trip back to Yaw 2 years ago, so I've been borrowing carbs ever since. Some have oil metering, some don't. Stupidly, I ran the car on the track on the fuel in the carb and lines that had no premix, (without pumping to the premix in the tank) and on a carb that had no metering to scrub in some tires, and poof! No starty! No compression.

I superheated the edges of the apex seals, and when they cooled, they were bananas. So i did my first rebuild. As the apex seals were the issue, that's all that I replaced, except for the usual stuff that gets destroyed on disassembly, and as a result, the cost was well under $500, I'd guess. (I measured everything else once open and it all measured fine).

So, moral of the story is: operator error, caused by allowing outside varibles to change my game.
2nd moral: A blown motor isn't always a multi thousand dollar problem.