BMW R 28


Allgemeine Informationen

Foto aus "BMW Einzylinder richtig angefasst" (S. 154 Bild 15) von Ernst "Klacks"Leverkus. Einer von drei Prototypen der R 28. Als Kundenkreis waren hauptsächlich Behörden angepeilt. Es gab 3 verschiedene Prototyp-Ausführungen: R28a mit Langarm-Vorderradschwinge, R28b mit Kurzarm-Vorderrad­schwinge und die R28c mit Telegabel, wie sie später in den großen /5 Modellen verbaut wurde. Das Projekt wurde dann aber gestoppt, weil niemand mehr Einzylinder haben wollte.

Zitat:The BMW R28 is a development of the production touring motorcycle model R27 for the requirements of the Defense Ministry, Frontier Guards and Cross Country sports enthusiasts. I understand that all vehicle specifications for the Military were achieved except for the weight and it appears likely that BMW was not prepared to design a totally new motorcycle without guarantees of getting the order from the authorities. Several versions of the R27 were also tested with normal Earles Forks, modified Earles Forks and with telescopic forks. Some of the spec. required: Frame with rear wheel suspension; Telescopic fork; Cross country tyres; Suitably large fuel tank; Seating for 1 - 2 persons; Sturdy sump guard; Oil moistened air filter (oil bath?); Brackets for two panniers; Holder for dispatches; High level exhaust system (Note the photo shows a low level system fitted).

Folgende Tabelle wurde entnommen bei:

Start of Production 1964
End of Production 1964
Numbers Produced Pre Production only
Motor Type Modified production single cylinder engine: vertical air cooled 4 stroke. Aluminium crankcase, cast iron cylinder, aluminium cylinder head with inclined valves. Built-up steel crankshaft with self aligning ball and roller main bearings. Chain drive with tensioner for ball race mounted camshaft. Valve operation by pushrods and rockers. Anti vibration flexible engine mountings
Bore x Stroke 68 x 68 mm (2.67 x 2.67 in)
Displacement 245 cc
Max Power 18 hp at 7,400 rpm
Compression Ratio 8.2 : 1
Valves OHV
Carburation System Rubber mounted slide type carburettor with long inlet tract and waterproof enclosure. Oil damped air filter
Engine Lubricating
Lubrication by gear pump in sump
Power Transmission  
Gearbox In unit with engine. Gears with robust sliding dog engagement and shock absorber
Clutch Single plate dry clutch with diapragm spring
Number of Gears 4
Shifting Foot lever
Gearbox Ratios 5.33 / 3.02 / 2.04 / 1.54
Rear Wheel Ratio 4.5 : 1
Rear Wheel Drive Cardan shaft fully enclosed in oil bath swinging arm with heavy duty rubber sealing. Maintenance free spiral bevel gears with constant tooth angle
Electrical System  
Battery 6 volt 12 amp hour
Alternator 90 watt alternator mounted on front of crankshaft. Vibration free voltage regulator
Ignition Centrifugal ignition advance mechanism. Camshaft driven contact breaker
Misc. 160 mm diameter headlamp with parking lamp, lighting switch and tachometer. Combined tail / brake / number plate lamp. Horn, trafficators
Frame Closed, electric welded double loop frame of steel, particularly suitable for high speed use. Taper roller steering head bearings
Front wheel suspension Telescopic forks (developed from BMW R25/3) with hydraulic damping and travel of 126 mm.
Rear wheel suspension Rear swinging arm with two maintenance free taper roller bearings and hydraulic dampers. Travel of 105 mm. Short wheelbase and high ground clearance
Misc. High level cross country type handlebars with clutch and brake controls. Sports handgrips. Friction steering damper. Foam dual seat for 1 - 2 persons
Wheels Full width aluminium hubs with steel brake linings
Wheel rims 2.15B x 18 rims
Tyres, Front 3.25 / 3.50 x 18 Cross Country
Tyres, Rear 3.25 / 3.50 x 18 Cross Country
Brakes, Front Drum brake 160 mm x 35 mm/ 6.29 in diameter, full width. Swept area of 194 cm sq
Brakes, Rear Drum brake 160 mm x 35 mm/ 6.29 in diameter, full width. Swept area of 194 cm sq
Length x Width x Height 2080 x 790 x 1010 mm
Seat Height
(Ballasted 75 Kg)
785 mm
Ground Clearance (Ballasted) 170 mm
Wheel Base 1320 mm
Weight - Ready for Road (Full Military Equipment) 155 Kg
Max Gross Weight 375 Kg
Weight Disribution (F/R) at Max Gross Weight 150 / 225 Kg
Fuel Consumption 3.5 litres per 100 Km at 80 Kph
Top Speed 105 Kph