Thanks for the reply. Actually it looks very much like a R90S until you look more closely. The DO paint is new and everything else is fresh including the repainted frame. Based on owner description these are the particulars:
Frame--77 R100S
Engine--78 R100 cases, crank, rods, with flywheel lightened and balanced
Transmission--77-R100 torn down inspected and new shifting components
Carbs--32mm Bings
Heads--R100/7--not sure what year but they have the rocker arm mounting scheme used used until end of production in 1995
Cylinders--R90/6--with R90S pistons and Hastings rings
Final drive ratio--3.0:1 (33/11) same as R90S.
Wiring harness--78-R100RS
Instruments--R100RS ( speedometer, electronic tachometer, volt meter, quartz clock)
LH switchgear--R90S
RH switchgear--R90S
Top starter/engine cover--R90S
Mirrors--short black from 85 from R80
Exhaust--not sure but probably reproduction, looks new
Front brake rotors--Italian made Gramicca
Calipers-- R90S rebuilt
Master cylinder--85 15mm handlebar mounted BMW direct master cylinder
Rear shocks--Works Performance street tracker
Front forks--stock with RS springs and a 2nd anti dive spring in the last 1/3 of travel
Top fork tube support is from San Jose BMW and adjustable Telifix adjustable upper fork slider
Front wheel--Brand new spoked type used on all 1981 bikes
Rear wheel--OEM rear R90S with new spokes, bearings, polished
Tires--New Continental high performance Bias type
That's about all I know right now until I get my hands on the bike. It looks brand new in pictures. My definite plans for the future are new Delorto 38mm carbs and to raise the displacement from 900cc to 1000cc's and the compression to 10/1. Dual plugging the heads is probably also in the future when the Moteren Isrial 1000CC kit is installed. Not sure what else until I get a feel for the bike.