R100 Years Produced - Flywheel Changes

[geezergolfer56]

I'm looking into an 1980 R100...with no suffix...just an R100. I believe they were made from 1980-1984. My question relates to the engine changes made in 1981. Did they make these bikes for one year with the heavier flywheel and points and then switch to the Nikasil cylinder liner, the "clutch holder" for a flywheel, electronic ignition, and the other changes for the remaining three years? Does anyone have in depth knowledge on this? Thanks in advance for your help.

 

[20774]

I don't know about "in depth" but in looking at the part numbers, the flywheel changed beginning with the 1981 models, so probably bikes built in September 1980 to start. My '78 R100/7 has a heavy flywheel with part number 11221336380...fiche says "up to 9/1980". A 1980 model R100T has the same part number. For a 1981 R100T, no flywheel shows on the crankshaft portion of the fiche. I had to go to the clutch images to find the carrier. Along with the flywheel change, the transmission input shaft also changed.

None of us were BMW technicians on the assembly line so it's hard to say what the exact cutoff date was. It should have been September 1980. What did BMW do with spare parts at these periods of change? What if they ran out of pre 1981 parts but they still have 1980 bikes on the line. I'm sure some small items might have been put on bikes on either side of the date. But for the tools needed for such major parts as the flywheel and transmission, I suspect that a hard date was used because the technicians had to stop doing it one way and start with the new way.

 

[melville]

The September changeover date for most German stuff comes after August, when most of Europe is on vacation. Most factories have a smaller crew on hand in August, setting up the next year's production. Especially for big changes like the 1981 flywheel and trans updates.

 

[lkchris]

1980 bikes are "interesting."

It used to be the BMW parts system did not recognize existence of 1980 bikes.

I think for the most part they had the one year points in a can ignition system, still the old forks with ATE brakes, still the heavy flywheel, but perhaps the new pancake air filter. Pretty sure not the new clutch, but otoh the engine case with pancake filter looked like the new one, new front cover styling, etc.

R100 doesn't mean much ... its a naked bike, no fairing.

from 1977-1978 they were called R100/7
I think from 1979-80 they were called R100/T
From 1981 on they were called R100

Only in the first two years were the motors and driveline different than other models.

The R100/7 had lower compression, smaller valve heads, and smaller carbs and different rear drive ratio.
From 79 all engines and rear drives were the same in all models in a given year. Compression was reduced for 1981, ignition finally became electronic, and the light clutch arrived. Exhaust was dual crossover.

When RS and RT returned in 1987, there were lots and lots of differences.