Thanks for the response. We've got it narrowed down to early 50's Japanese but that's about it. I had no idea there were over a thousand Japanese mfgrs back then. Doesn't really fit with the board so it may disappear.
Jesse, a bunch of us have been trying to figure it out. If ya look around at early 50's Jap stuff, there's a ton of Brit lookalikes. Dead-ringer lookalikes. Triumph, BSA, Norton engines especially. It never ceases to amaze me just how little I know.
jap bike with plunger frame ??? those crash bars are specific to that bike too. switchs look jap dont spose youve removed any bolts to check threads .. push it upside down the box might give clues under neath...made in japan!!
Friday, the bike's in AZ and I'm in WI. Long way from here. I'll ask my friend about threads but I'm sure they'll be metric. Having looked around, there were lots of plunger rears on early 50's Jap stuff (which surprised me a bit also).