Engine Trouble phantom engine problem?

I have a 66cc HT from Ebay with about 300 miles on it. I'm running on a 32:1 mix and have made no mods. A few days ago my engine seized up at 32 miles of a 34 mile trip. It started making a squealing sound and the motor died almost immediately. Today I took it apart and don't see anything obvious that would cause this. No scratches on anything. There are a few small areas where it looks like some oil got too hot but that's the only thing I can find. I'm wondering if excessive heat alone was my problem and what would happen if I put it back together and ran better oil perhaps? Used Pennzoil 2-stroke oil.

that squealing sound *should* have left a mark somewhere, but it may be in the bottom end

you should check everything from wheel bearings forward thru chain and clutch to crank before starting it again (and hope you find something other than the main bearings gone bad)

20:1 is best for regular oil. 30:1 is good for synthetic or semi-synthetic oil.
if there is no bearing abnormalities then:
look and see if there is any piston aluminum that transferred to the cylinder wall. use sandpaper to remove it if so.
If you have a high compression head then replace it with a standard head. the high compression heads cause a lot more engine heat.
read up on jetting and try a richer main jet.

if the primary gears retaining screw backs off then that gear can contact the right engine case and make a noise and act as a brake.

I recall that once I had a noise like that - turned out that the case screw that sits under the clutch was loose and was backing out to where the head was almost worn off - replaced it and tightened all of them and engine was fine

Pull the cover with clutch arm off, and see if the chain is binding. A very common problem on these engines. If you find rub marks on the inside of cover, take a dremel or file and clearance it.