I have been following this thread and I am going to start with a caveat. The XYZ 53cc twin is my first gas engine. With that in mind, after reading the flying giants thread, I mistakenly put a 22x10 on my engine for break in. It had no problem with it at all. Also, this weekend, I put a 20x10 on and easily tached the engine in the high 6700 and it is still running pretty rich. Just my experiences that I wanted to share. I hate tuning this engine because the needles are so close to the prop. I have been told that is typical of gas engines but it makes absolutely no sense. Tune high needle, start engine, check rpms, turn off engine, start over. Crazy !!!

My question, what lead you to figure out the bearings did not fit? I am concerned with my engine that this may be an issue. It starts fine and runs good. Anything I can check without pulling the engine apart?

Take the prop tips and push one and pull the other - alternate and determine if there is slop in the crankshaft?

hello squirrel;

It sounds like your engine is okay, all good to go? You were one of the lucky ones, with a good engine?
Except the ignition, of course.

It you move the propeller back and forth when the pistons are at the bottom; then there is no compression.

You should not feel any "resistance" in the crankshaft. No "lugging" resistanse. Difficult to explain....

Take any other engine, do the same, then compare? Did you ever have an engine where the bearings got rusty?
It's the same feeling. Not good. Hopefully you don't have this problem.