- Model: R100 S
- Year: 1980
- Street: 8150 SW Barnes Rd Apt G307
- City: Portland
- State: Oregon
- Country: United States
- Zip/Postal Code: 97225
- Listed: December 15, 2017 10:27 pm
- Expires: 58 days, 18 hours
The R100S’s growth from a 600 has not been entirely without problems, most of which seem to have been recognized and solved.
One particular difficulty came from the very compactness of crankcase that provides the engine its strong foundation. Due to the opposed motions of the BMW twin’s pistons and its high crankcase compression ratio there always has been in it a tendency to huff, puff, and blow its oil out on the ground.
In the R100/S’s immediate relatives this huffing was controlled with a simple spring-loaded flapper disc, which kept the engine from inhaling a volume of air equal to its own displacement with each 180-degree rotation of its crank and then exhaling much the same volume of oil mist when the pistons returned to bottom center.
The flapper disc permitted only the exhale, which didn’t amount to much when not preceded by an inhale–in the smaller-displacement BMWs.