BMW R 51/3
The BMW R 51 /3 is a 1951-1954 produced in 18,420 piece sidedare compatible two-cylinder motorcycle manufacturer BMW with 500 cc boxer engine with 18 kW ( 24 hp ) and shaft drive. The selling price bertug 2750 DM Together with the simultaneously published BMW R 67 it was the first major BMW Motorcycle new development after the Second World War, 51 ( 1938-1940 ) and was followed only in 1950 produced R51 / 2 BMW R.
Design Features
The double-cradle frame is made of steel tubing welded with side-mounted ball heads for the sidecar operation. The S 350, better still, the TR 500 of Steib is a matching sidecar for sidecar operation is a modified (shorter ) translation of the shaft drive required.
Fenders and tank are made of sheet steel, the engine block, transmission and the cardan transmission housing made of cast aluminum. As with the previous models BMW R 51 /2 and BMW R 51 serve two half shafts of the motor bearings in rubber bushings of the frame. The " fishtail " mufflers are attached with clamps directly to the motor shaft and the frame and in 1954 replaced by a modern form.
Motor
The engine of the R 51/ 3 is compared to the same power predecessor of R 51/ 2 fully redeveloped with only one gear driven camshaft to the crankshaft; the predecessor engine BMW R 51/2 had two camshafts, which were driven by chain.
The engine block is like the transmission and the cardan - cast aluminum housing. The motor is equivalent to previous models BMW R 51 and R 51 BMW / 2 on longitudinally-mounted two-cylinder boxer, four-stroke engine with the outside, above the cylinders in protective tubes in chromed steel bumpers running ( OHV ). These bumpers actuate the rocker arms in the cylinder heads that turn the hanging valves. The rocker arms, piston pins and connecting rods are mounted in bronze bushings; The crankshaft runs in ball bearings. The gear oil pump is located behind the front housing cover and is driven by spur gears.
Transmission
On the rear tailshaft the heavy flywheel sits ( with ignition marking ) that receives the single dry. The clutch thrust bearing is operated by a push rod passing through the hollow main shaft of the four -gear transmission. This model has the classic curved chrome lever occasion. Left a pedal and right hand shift lever according to the then- standard DIN 73005 is attached, which called (until March 1970): "prescribed foot gear for all motorcycles addition, a hand lever must for operating the circuit under special conditions of motorcycles with 250 cc and. be about yet. "
Ignition and alternator
On the front tail shaft sits behind the enclosure lid, the DC - alternator of Noris with charge controller. The ignition system is no battery ignition, but a magneto ignition with centrifugal, and is driven by the camshaft. The motorcycle can still drive accordingly also with a dead battery (or without ), since the ignition current is generated independent of the battery. The lead-acid battery is mounted on a unpackaged holder under the saddle.
Carburetor, air filter
The carburetors are Bing float chamber carburettor with conical needle in a circular slide and 22 mm passage cross section. The wet air filter element sits on the gearbox, a steel net, where the dust settles when air, and which is washed for maintenance purposes and coated with oil.
Drive
The drive train at the transmission output has a resilient torque transmission element, a fabric -reinforced rubber, four- hole disk ( flexible disk ). It is pushed on Zweifingerflansch transmission and transmits the torque of the transmission output shaft to the two finger receiving the propeller shaft. The Hardy disc has circumferentially due to the high centrifugal forces of the rotating rubber wheel a chrome steel ring.
The high-gloss chrome-plated propeller shaft is not sealed. The angle gear is attached to the universal joint of the propeller shaft is covered against dust with a chrome screw cap. Against this runs a rotating screw with shaft seal rubber that resists dirt from the universal joint keeps.
The bevel gear with 90 ° deflection is a bevel gear with hypoid gearing, so that a heavy gear oil for high flank pressures ( hypoid ) must be used.
Wheels
In 1954, the two-color painted steel rims (3 × 19 ) were replaced with alloy wheels and semi-finished steel hub brakes ( " can lid brake" ) by wide aluminum full brake hubs, after 1952 the front brake with the help of a duplex design was improved. The brake drum diameter remained unchanged as well as the tire size 3.50-19 with 200 mm.
Specifications
- Brake type front duplex from 1952
- Rear brake type Simplex
- Greatest width 790 mm
- Maximum length 2130 mm
- Saddle height 725 mm
- Ground clearance 103 mm
- Wheelbase 1400 mm
- Permitted total weight 355 kg solo
- Permitted total weight 600 kg trailer
- Empty weight with orig. BMW sidecar 320 kg