new piston problem

To be honest if you take your time, use plenty of lube, make sure the ring end gaps are correctly positioned and don't "force" anything you should be fine. I would tend to agree that "too little" clearance is unlikely and a little excess will only result in reduced compression and possibly a little smoke from the exhaust. Be careful with your carb assembly so there are no air leaks and if it doesn't "feel right" stop. Giving it a good "thrashing" will never resolve issues  - (although it may make you feel better at the time)

haha...I'm not a thrasher.  The carbs are one thing I'm very experienced at, having done far too many times.

But now JBM is suggesting my brand new (14 miles) slider rubbers may have swelled from exposure to ethanol in fuel...they are not snug on the slider and I certainly never used carb cleaner near them. Only 14 miles on them....but they fall right off the slider with hardly a touch. It never ends. TBH I don't know if there is ethanol in my fuel but I only buy it at on place so I will check.

Nope, just called em there's no ethanol in the fuel I use.