That's a very interesting engine you happened to see, and seems like one worth giving some thought to.
It is obviously a Honda Cub based clone engine, of which there are many.
What's particularly interesting about this engine is that in place of a kick start shaft, there is now a cottered pedal crank. I really wish there was a picture of the other side of the engine! If my memory is correct on this, the kick starter shaft on these little Honda engines is just a plain (or maybe bushed) bore in the case and cover. Being almost certainly Chinese made, I doubt this engine would have improved this to ball bearings, and wouldn't likely hold up to any serious pedaling. Probably good enough to start the engine and be legal though!
With a 2 speed automatic and some sort of a high/low box as well, this certainly sounds promising for a motorized bicycle application.
Edit:
From this vendor, I see that $299 plus $40 shipping gets you a totally bare engine with no carb/intake/filter or exhaust etc. If anyone happens to find a cheaper source for this engine and/or one that is more complete, please post a link.
The Honda CRF50/XR50 etc. horizontal clones are really common, this one only somewhat different with the inclusion of the pedal system - I really doubt that's a shoddy modification however & suspect it's far more likely to be simply another clone of a four stroke moped, of which only seem uncommon stateside.
As for the durability & pricing, it's something to consider that it's complete with an actual transmission built for a 'ped instead of some costly aftermarket conversion made with bicycle parts... that alone makes the difference between something like this and even the cheapest of two stroke kits, throw in it's a four stroke w/electric start for some icing on the cake lol
I'm not defending or vouching any particular vendor, although I would suggest calling and asking what's included as the Lifan CRF50 clone (3sp autoclutch) I ordered was pictured the same but included the carb etc., everything but the electricals (CDI reg/rec etc). The moped/pedal case type is somewhat uncommon but this engine class isn't and the price seem pretty much right, even if ya hadta pick up a carby or whatever.
I just think this is a great engine type for our application, reasonably priced & reliable I'd like to see more try it. This is
nothing like the in-frame two stroke "quality" yet it's roughly the same cost overall and yet an even better selection of aftermarket goodies - the only real issue is it's somewhat wide & horizontal, a difficult build for anything other than a chopper or recumbent.
Here's my Lifan CRF50 clone 3sp autoclutch build if you're interested;
engine start:
http://youtu.be/aQXKnt9hZzU
build & run:
http://youtu.be/bNLTLRx8sTI
...and a somewhat dated thread about the horizontal fours, including some chopper build links;
http://motorbicycling.com/showthread.php?t=19630