BMW R 67/2
The BMW R 67 is a sidecar-compatible two-cylinder motorcycle from Bayerische Motoren Werke with a displacement of 600 cm³ and a rated output of 19.5 kW (26 hp). When it appeared in February 1951, it was the first major new BMW motorcycle development after the Second World War, together with the 500 cm³ parallel model BMW R 51/3 ; the R 51/2 model produced in 1950 still had the pre-war engine with two chain-driven camshafts. After 1470 copies of the R 67 were produced, the R 67/2, with its rated output increased by 2 hp, came out in December 1951; it was produced 4,234 times by 1954 and was the fastest German touring motorcycle until the appearance of the 35 hp BMW R 68 sports model.
The typical appearance of the R 67 included the so-called "fishtail" mufflers, which disappeared as part of the model upgrade in 1954. The R 67 and R 67/2 were mainly driven with a sidecar, the R 51/3 were often driven solo, benefiting from the good torque curve.
The indirect predecessor of the R 67 was the pre-war model BMW R 6 or the BMW R 66 (1938–1941).
Design features
engine
As in the previous models, the engine is a longitudinally installed two-cylinder boxer four-stroke engine with bumpers running over the cylinders in chrome-plated protective tubes, which operate the hanging valves via rocker arms in the cylinder head . Like the two connecting rods, the rocker arms are mounted in bronze bushings. The central camshaft is driven by the crankshaft via a gear set running in an oil bath. The oil pump is a simple gear pump behind the front housing cover and is driven by the spur gears through reduction .
The compression ratio of the R-67 engine is 5.6: 1, that of the R-67/2 and R-67/3 engines 6.5: 1.
Ignition and alternator
The splash-proof encapsulated 45 / 60W direct current alternator with charge regulator sits on the front crankshaft stump behind the aluminum alternator cover . On the rear stump of the crankshaft sits the heavy flywheel (with the ignition timing mark that can be seen in the peephole), which holds the dry single- disk clutch . The ignition system is not a battery ignition, but a magneto with centrifugal adjustment, driven by the camshaft. The motorcycle can therefore also drive with an empty or without battery, since the ignition current is generated independently. The lead accumulator is attached to a holder under the saddle without being encapsulated.
transmission
The gearbox type 250/4 is based on the version built for the BMW R 5 since 1936 ; it is a claw-shift two-shaft four-speed gearbox with a shock absorber and helical gears for 4th gear only. The input shaft runs at crankshaft speed, the output shaft at cardan shaft speed. The transmission is shifted with the foot on the left, first gear below. The automatic gearshift and gear ratio essentially correspond to the structurally identical transmissions of the other two-cylinder models of the post-war period with straight-travel suspension . All bearings used are standard parts and are still available today. A weak point of the transmission is the wear and tear of the two switching disks for the 1st / 2nd. and 3rd / 4th Gear, which manifests itself in gears jumping out under load. The clutch is operated with a thrust bearing via a push rod that runs through the hollow main shaft of the gear unit. This model has the classic curved chrome kick starter lever. On the 4-speed gearbox there is also a manual gearshift lever on the right-hand side of the motorcycle, with which the gears can be shifted manually. The reason was probably to make it easier to find the idle while stationary. Problems with the clutch construction are the relatively weak 6 compression springs and thin pressure disks, which tended to warp and the clutch slipping as a result. Only the redesign of the clutch of the R50 / 60 series brought a clear improvement, which eliminated these weak points with a disc spring and a much more stable pressure plate (at the time, a useful and popular conversion). The position of the clutch release lever next to the Hardy disk was also problematic in terms of construction.
Carburetor, air filter
The two carburetors are classic 24 mm Bing float chamber carburetors with a conical needle in the round slide. The wet air filter element sits on the gear housing. The connection of the chrome-plated intake pipes between the air filter and the carburetor is made by rubber sockets that are attached to the carburetor. The air filter is embedded in the gear housing. It is made of a steel mesh that is soaked in oil, on which the dust sticks when the air is sucked in.
drive
The drive train requires an elastic torque transmission element at the transmission output. For this purpose, a black rubber four-hole disk ( Hardy disk ) is pushed onto the two -finger flange of the gearbox, which transfers the torque from the gearbox output shaft to the two-finger mount on the cardan shaft. This hard disk is equipped with a chrome ring. The cardan shaft to the rear wheel is chrome-plated and runs freely; it is attached to the bevel gear in the cast aluminum body with a cardan joint . The deflection gear is an angular gear with Klingelnberg teeth and 90 ° deflection. The gear wheels of the deflection gear run in a special heavy gear oil for high flank pressures (hypoid oil). As with all other two-cylinder models with straight travel suspension, the weak point of this final drive was the too small and too weakly designed drive teeth for the rear wheel, which also led to high wear on the rear wheel hub. The inadequately sealed and maintenance-intensive universal joint was just as problematic. The R50 / R60 series also brought significant improvements here. Rear axle ratios R 67 and R 67/2: 32: 9 solo, 35: 8 team.
bikes
The duplex brakes of the R 67/2 were initially built as steel half-hub brakes and from 1954 as wide aluminum full-brake hubs. Compared to the predecessor model R 67 from 1951 with simplex brake, this change in the front brake brought a considerable improvement in the deceleration values. Along with the transition to solid aluminum hub wheels, the brake anchor plate was also slightly changed and the brake shoes widened by 5 mm (R 67/2 and R 51/3). The transition to aluminum hubs also resulted in a slightly modified cast body for the final drive housing and front brake anchor plate. The older steel hubs with double-thick spokes were preferred in sidecar operation.
BMW R 67/3
For only about a year around 1955/1956 BMW delivered 700 sidecars under the designation R 67/3, which are based on the type R 67/2.
Technical data of the R 67/2
- Two-cylinder four-stroke engine
- Bore 72 mm, stroke 73 mm, displacement 590 cm³
- Output 20.6 kW / 28 hp at 5600 rpm (R 67: 26 hp at 5500 rpm)
- Top speed solo around 140–150 km / h, team around 100–110 km / h
- Consumption approx. 4–5 l / 100 km solo, 5–8 l / 100 km combination
- Unladen weight ready to drive 192 kg
- 3.50 × 19 inch tires
- Rear tires on 67/3 with BMW special sidecar 4.00 × 18 inches
- greatest width 790 mm
- greatest length 2150 mm
- Saddle height 725 mm
- Ground clearance 103 mm
- Wheelbase 1400 mm
- permissible total weight solo 355 kg
- permissible total weight as a combination 600 kg
See also
Web links
- BMW R 67/2. In: BMW history. BMW AG, accessed on June 30, 2016 (dossier of the BMW Group Archives).
- Manual BMW Motorrad R 51/3 R 67. In: BMW History. BMW AG, December 1951, accessed on June 30, 2016 (manual with pictures, 85 pages).
- Spare parts list for BMW motorcycles R 51/3, R 67, R 67/2. May 1952 edition. In: BMW History. BMW AG, May 1954, accessed on June 30, 2016 (spare parts list with pictures, 32 pages).
Individual evidence
- ↑ Price list no. 2/1951. In: BMW history. BMW AG, October 1951, accessed on June 30, 2016 (document in the BMW Group Archive).
