THE BMW R G/S The Monolever generation

The 1980-1986 R80G/S

The first of September 1980, in Avignon (a southern French city), a new type of bike is born. The first big trail bike is on the market. It is the G/S, where G is for Gelände ("offroad" in German motorcycle vocabulary) and S for Strasse ("street" in German). This bike, with a mono arm rear suspension called monolever, is the result of the numerous years of experience of the BMW enginers.

It is derived from :

• the R series (for example a 1974' BMW R90S, ~ 28 kB jpeg) touring motor bikes;
• the "Six days" enduro prototypes:
  
  The BMW enduro team of 1979 (R.Witthöft, L.Perez, D.Beinhauer, K.Fischer, H.Schek, R.Schalber)

The principal qualities of the R80G/S :

• a very low weight for a big trail bike (191 kg);
• the strong and "tireless" (if we watch the oil level) boxer (or flat-twin) engine of the BMW bikes R series.
  Engine :
  • 798 cm³, 84,8mm x 70,6mm, 50 hp (37 kW DIN) at 6500 rpm, 56,7 Nm at 5000 rpm, Compression: 8,2:1, 2 Bing carburators 32mm, 5 speeds.
• a good load capacity;
• a large number of optional parts (bags, tank,...).

Technical info

• The monolever

  The mono suspension arm contains the drive shaft. The system is enclosed with oil inside to lubricate the shaft. The rear wheel is fixed by 3 lugnuts.

• Electrical wiring diagram
  
  • click here for the electrical wiring diagram (.gif file, 96kb);
  • click here for the electrical wiring diagram legend (.txt file).
• Owner manual on-line (pages made by Donald Massyn).

The R80G/S lineage

• 
  the rare R80ST, a road oriented R80G/S, may be the best twisty road bike BMW ever built. The differences between a R80G/S are :
  • the original chrome engine protection bars;
  • a stainless steel exhaust with a black cover plate;
  • the left side panel (which can create problems for mounting luggage racks made for the G/S);
  • smaller chrome-plated handlebars
  • a larger oilpan (standard road model) and no bash plates;
  • no kickstarter;
  • the wheels : 100/90 H 19 and 120/90 H 18 (instead of 90/90 T 21 and 130/80 T 18);
  • a compression ratio of 8,0:1 instead of 8,2:1
  • a rear shock with smaller travel (153 mm vs. 170 mm);
  • the front of an R65 : (headlight, console, mudguard and forks with small modification (a rebound spring that the R65 doesn't have);
  • the tank (R65 style) and tank cap;
  • the weight : 198 kg;
  • and beautiful metalic (crimson red or grey) paint with white stripes.
  
  
• the racing prototypes used in the Paris-Alger-Dakar rallies.
  
  
• In 1984, BMW present the first "Africa" enduro bike, the R80 G/S Paris Dakar.
  

  	The differences vs. a R80G/S are : a bigger steel tank (32 lit./8.9 gal.) with Gaston Rahier's signature on it; a solo seat with a fixed luggage rack (to get under the seat, all the seat/rack unit have to be removed); no plastic side panel (the battery is visible); a stainless steel exhaust with a black cover plate; a 12v/20Ah battery in place of a 12v/16Ah; the weight : 205 kg; engine torque value of 58 Nm at 4000 rpm vs: 56,7 Nm at 5000 rpm.

• During the period 87-90(life time of the first version of the paralever GS), the first G/S version continues with a smaller engine (650 cm³, 82mm x 61,5mm, 27 hp (20 kW DIN) at 5500 rpm, 43 Nm at 3500 rpm, Compression: 8,4:1, 2 Bing carburators 26mm, 5 speeds), it's the R65GS. It is exactly like the R80G/S except for the chrome exhaust, the GS mirror, the battery (12v/20Ah vs: 12v/16Ah) and the weight : 198 kg.