Drivetrain Service Bulletins

Service bulletins related to engine, transmission, driveshaft and final drive will be posted here.  In general, I started with the earliest ones first, but you will find that the order isn’t exact.  Long story.

Many of the older service bulletin titles will show “engine” first, and that is my shorthand method for the entire drivetrain.

Protection for the transmission coupling flanges June 1952

Transmission oil return improvements July 1952

Shorter cylinders R67/2 & R68 Nov. 1952

A clutch issue, all models, Clutch Center Plate Dec. 1952

R25, R25/2, final drive ring, engine, driveshaft ring Nov. 1952

The out of stock R24 cranks replaced by R25 cranks Jan 1954

R25, /2, /3 rubber U-joint, engine, driveshaft rubber July 1955

R50 & R69 driveshaft cover, engine, driveshaft Sept. 1955

R26 final drive oil seal, engine, final drive seal March 1956

Magnetic drain plug, engine, magnetic plug April 1952

R25/2 overheating , engine, overheat Sept. 1952

R67/2 pistons & rings, engine, piston June 1953

Polishing covers overheats the engine, engine, polishing May 1952

Motorcycle & Isetta light alloy rod, engine, rod Jan. 1957

R25/3 run in oil consumption, engine, run in time March 1954

Summer engine oil, engine, summer oil April 1956

R25/3, R51/3, R67/2 & R68 transmission leak, engine, transmission Oct. 1954

BMW, Isetta & Limousine valve guide, caps & locks Nov. 1959

Sidecar final drive ratio, engine, FD sidecar ratio Jan. 1963

R27 final drive ratio change, engine, R27 final drive ratio Feb. 1963

Increased R27 piston clearance, engine, R27 piston July 1963

Page 1, R27 oil pump, engine, R27 oil pump pg 1 Feb. 1964

Page 2 R27 oil pump, engine, R27 oil pump pg 2 Feb. 1964

R60-R69S clutch spring change, engine, clutch spring June 1964

Main bearing error, engine, main bearing error April 1964, related to the next bulletin below

Twin strange engine/transmission sounds, engine, twins, crank, transmission sounds Sept. 1964  To see the dial indicator recommended to dealers, here is the link.  tool, Dial indicator , April 1964

Main bearing plate change, engine, main bearing plate Feb. 1965

U-joint on driveshaft failures, engine, U-joint Feb. 1965

Piston clearance chart, engine, piston clearance April 1965

Pushrod change, engine, push rod Oct. 1965

Speedo cable drive gear mod, engine, speedo drive gear Oct. 1965

Cylinder base gasket, engine, cylinder base gasket Nov 1965

Removing alloy exhaust nuts bulletin 78-4

Cylinder base gaskets bulletin 11-79-13NS

Engine oil cooler bulletin 4-79-4NS

Piston ring seating bulletin 2-78-5 N

Engine ID change, 1070 R, July 1979

Synthetic oil approved, 1079 R, no date

5-speed gearbox broken pawl spring  163 M, Jan 1975

/6 Flywheel bolt size increase 164 M, Jan 1975

Cylinder head and gasket change 1045R, June 1978

Piston wrist pin changes, 1047 R, June 1978

Gear shift mechanism improvement, 1049 R, June 1978

Cylinder base spacer, 1057 R, Sept. 1978

R100RS oil cooler installation, 1060 R, May 1979

Low oil pressure on all models, 1061 R, March 1978