I used to own a '81 C70 (Passport) which is just a jazzed up Super Cub with electric start for the U.S. Market. Mine had the original engine in it, which is what the Lifan engine is a copy of, in various displacements. A 110cc will bolt right in. These engines have a strange rotary shift pattern, completely different from the 1 down X up like a motorcycle. But the worst thing about them is they have no clutch. If you get stuck at an intersection with a stalled engine, and a lifted truck behind you blowing the horn and inching forward, you can't just pull in the clutch and push the bike off the road. You have to first find neutral, which can take a while under such circumstances. The pattern was like N-1-2-3-4-N-1-2-3-4 over and over again.
I won't spend more on a bike than I think it's worth, but if it's a good deal, I don't seem to have a problem buying bikes I don't need.
2002 Vulcan 750, 2013 Royal Enfield B5
2001 XT225, 2009 Genuine Stella
1980 Puch moped