I don't have a problem with 2 strokes, or at Least I didn't until recently. I have loved 2 strokes all my life. But, not very long ago, my '79 Yamaha YZ250 seized up on me, for no apparent reason, premixed at 40:1, all jets clean, no air leaks, proper A/F mixture, completely destroyed the top end, and I cannot find another one anywhere. Then my Tecumseh TCII seized up on me, and broke a ring, again for no apparent reason. Then the 2 stroke engine in my brand new Genuine Stella scooter seized up on me, with less than 400 miles on it. This was an oil injected motor. It was repaired under warranty, but I am now afraid to trust it to go very far from home with. My Yamaha Vino 125 4 stroke scooter has 14,000 completely trouble free miles on it, most of them at WOT, and still runs like new, and the compression is within spec for a new engine.
I have ridden 2 stroke motorized bicycles, mopeds, and dirt bikes all my life without any problems, other than with some of the mopeds that were seriously modded for more speed, but you have to expect that.
All 3 of the 2 strokes that blew up on me recently were stone stock and running fine.
The other problem I have with a 2 stroke engine on a bicycle is that I now live in town, and 2 strokes are noisy. the Tecumseh could be heard a mile away, I had to wear earplugs to ride it, and it attracted all kinds of unwanted attention. I want a bicycle engine that will just purr along without causing any issues because of the noise. Not only does the noise irritate everybody, but it tells everybody that you are riding a motorized bicycle, something else you don't want to do around here. Where I live, motorized bicycles are legal, but hated by almost everyone, especially the spandex crowd, and there are tens of thousands of those in my area. They can't stand the idea that we are allowed to ride in the bike lanes with them, and cagers hate us because when traffic is backed up for over a mile, we can just ride right by them in the bike lane, and not even have to pedal.
Roland Bosma from Spooky Tooth Cycles helped get the law passed in AZ making motorized bicycles legal, and I thank him for that, but they are still hated by almost everyone. I have been run off the road, called every name in the book and then some, and had all kinds of things thrown at me, including glass bottles. It's gotten so bad I've started wearing a helmet and shoulder pads. Jerry.