http://www.bmbikes.co.uk/chassispages/e ... sis900.htm
Can you expand on your post "...the serial number isnt the same sequence as other american R90s i have noticed..."? What do you mean by that?
'78 R100/7 '69 R69S '52 R25/2
The 407 serial number is for ROW, (Rest of World) shipment.
BMW had two sets of numbers for those year bikes. 497 and 407. 497 numbers were for US production and 407 for everything else. It's debatable how a 407 serial numbered bike got into the states. Many came over from Canada.
Andy Pelc was a character for sure. He often punched his initials (AP) on bikes he sold so returning customer's would get preferential treatment on service needs. Look for it around the oil dipstick area.
You have an early bike for sure. (Mine is 4070926), from 11/73. I bought mine from the original owner in 1980, who says he bought it from Andy too (no AP mark on mine). And I've met a few other guys in the Detroit area who bought bikes from Andy claiming it was the first one he sold.
I noted C137 stamped in the engine case near the oil filler.
I stumbled on this information:
I spoke to Kari Prager of CAL/BMW Triumph on Oct 30, 2007 who told me Dave Golden of Dave Golden Motorcycles in San Francisco, added a private serial number to each bike sold. No one knows why.
I spoke to one other R90S owner years ago, John Gallagher of Danville, CA on Oct 28, 2007 who said he had the same situation with his R90S stamped C153, but it is likely all bikes sold by Dave Golden (see below) had the same stamping, not just R90Ss.
John said his bike was sold by Bavarian Cycle Works of San Francisco which was later absorbed by San Francisco BMW, a car dealer.