It is unlikely that the engine has no speed adjustment if it's on a lawnmower - but it isn't impossible. I've never seen one like that, though. Can you post pictures? A self-propelled mower with no speed adjustment would be awkward to manoeuvre, I'd have thought. More likely the control is missing, or not working, or you haven't found it yet.
Seems like it was made on 22 May 2000.
Despite that site I listed above saying it is OHV, the one in their picture is side valve, and the engine they are talking about is definitely side valve - here is the cylinder:
http://www.partstree.com/parts/?lc=briggs_and_stratton&mn=12H802-2640-B1&dn=09900002If that first site can't figure out whether it is side valve or OHV, their opinion on whether it has an aluminium bore obviously isn't worth much. However it looks to me to be just a run of the mill Chinese Briggs, with an aluminium bore. Glad yours has worked well - I don't see why it wouldn't, if they followed the Briggs drawings properly. I'm pretty sure the bad engines they've built were just a result of having to get their act together - the ones they didn't mess up were most likely just as good as a traditional American Briggs.
