47U or what the heck is this Barn Find?

[mike c]

  Looked at a barnfind this weekend.60's style hardtale chop. Extended springer, fair shape but the engine has me somewhat baffled. Left side case has serial# 47UXXXX.  Numbers appear to be original. Right side case is obviously Pan or Knuckle and it is all topped off with shovel heads and a Super B. Would it be possible to mate a U left side with a knuck right side? The base of the jugs hang out over the edge of the cases about  3/16" or so on the left side and the rear. Or do ya think its a nice number job?  The owner says it has a "B" grind cam which wouldn't be the case if it was a U-Model. Anybody got any ideas?  I mean  ?   

[Speeding Big Twin]

I don’t know exactly what’s involved in matching a U-series left case with a Knuck right-hand case but a factory-stamped 47U serial number should look something like the one below. Notice the 4 has an open top (not an open back) and a serif at the base etc. Also notice the two nubs above the number boss:



The case at below left is a 1940â€"48 U-series type and it has the two nubs. It has short upper reinforcement ribs, casting number 112-402 and a casting date code. The case to the right is a 47 Knuck and it has no nubs above the number boss, the boss is a different type and the area near the top case stud hole is recessed. The Knuck case has long upper ribs and no casting number or date code showing (casting info is inside):

 

Can you post photos of the bike? And a photo showing just the first few characters of the serial number? And check the belly numbers.     Eric

[mike c]

Thanks a bunch Eric! I'll be seeing the bike again this weekend and will try to take some pics of this thing.  Very fine info. Thanks again and Happy Trails. Mike C