This info is provided by Marko of Tomos fan page
The main Tomos factory in Koper city is about 100 miles away from my home, and yes, I've seen it up close. I also sending you a picture (sorry for bad scanning, I couldn't find a better one). The company is in a lot of trouble now because of "scooter invasion" in Europe, which erased the moped market completely (the only thing saving them are low moped prices and car components production).
Now about the BT50..Unfortunately it's not being produced in Slovenia for three years now (maybe Tomos Nederland still produces the BT 50N model). I don't know the reason, but my guess is that it's because of the legal limitations. Because it exceeds 49 km/h limit, it's put in the 50-125 cc class here and that makes selling a 14 year old design really difficult. Other guess is the production discontinuance of Italian components on the moped (Grimeca brakes and rims, CEV electrical equipment, instruments, seat, etc.).
But the most important thing that should be known about this bike is that it has remained the same for 14 years and has never been updated (I own a '89 S model and the last ones that came out were exactly the same). That's why it's got no oil pump, no seat locks and no E-starter (but this is not really necesary on a moped of this size), which are common on other mopeds. Engine is also a big problem. Without the reed valve it's very difficult to drive (it has a usable range from 6000 to 8000 RPM). Once your over 6000 it's great, but under that..farm tractor. If it just had the oil pump and the reeds, it would be perfect. It's also a bit small compared to today's mopeds.
Of course there good sides of this bike. First of all, the excellent frame (as on the ATX and CTX) which originates from Tomos racing bikes, good braking ability and very good gearbox, that makes no-clutch shifting (at high RPM, of course) safe and without consequences to the engine. Suprisingly, fuel consumption is very low (mine uses about 3l/100km), performance in acceleration and top speed is equal to modern scooters with Minarelli engines with blockades removed (such as Aprilia SR 50 or Gilera Stalker, Runner and others..). Although the BT is not currently being produced, the engine "lives on" in the ATX 50S cross model.
I found some technical info about the BT 50S (applies also to BT 50N, the difference is only in the bodywork):
Power 4 kW at 8000 RPM
About my page..I noticed that many people are interested in BT. Expect more on this topic. I hope I will be able to record a video (or at least some audio) before winter. I'm also preparing a report from the Technical museum of Slovenia where I took photographs of Tomos developments over the years.