BMW GS history
BMW introduced the R80GS and R100 GS (for Gelände Sport, Gelände meaning something between "country" and "field" in German) in 1988, and the Paris-Dakar version in 1990. Starting in 1992, the Paris-Dakar was re-designated the PD due to some legal conflict with the organizers of the Paris-Dakar rally for which it was named.
1988~1990
The GS is introduced, replacing the G/S. The US got only the R100GS, but an R80GS was sold in other markets. The major differences between the R80GS and R100GS are:
- the oil-cooler on the R100GS
- a small 'tombstone' windshield on the R100GS
- 798cc vs. 980cc. The R100GS got 40mm carbs in non-US markets while the rest got 32mm carbs.
The differences from the G/S are:
- Paralever rear suspension (185mm travel) and 40mm Marzocchi fork (225mm travel), resulting in...
- More weight and a longer wheelbase, allowing...
- Larger battery tray to accomodate large or small battery (large was provided).
- Stronger rear subframe with small rack
- Painted headlight/instrument nacelle (the G/S was generally matte black)
- 40mm Brembo dual-piston front brake
- New centerstand design (feet curved out)
- 17" rear rim, cross-spoked wheels allowing tubeless tires. Heavy, though.
- 6.4 gallon tank with two petcocks. US got a flush cap, EUR got a protruding cap with horizontal tube vent.
- No kickstarter, but available as an add-on. I think all Swiss bikes have the kickstart.
- Cable-operated rear brake.
Model year differences
In 1988
- All models were equipped with the high fender only. In the US, a rectangular fork brace was produced to allow the high fender to be mounted low.
- Introduction of the Valeo starter instead of Bosch.
In 1989
- The optional low fender appeared. This mounted with special bolts onto the existing curved fork brace and fork leg tabs.
- The attachment of the rear fender to the battery tray was modified
- A Gore-Tex insert was used on the instrument cluster to help prevent fogging
- Softer spring for rear suspension
- Change to lower left mounting of side cover
- New clutch throwout bearings (all BMW models)
In 1990
- Symmetric rear brake cam and shoes (was asymmetric)
- Improved rear brake lever (according to press release)
1990 Paris-Dakar
At first the components were only available as a kit, but for the 1990 model year the Paris-Dakar was introduced.
- Nylon tank (9+ gallons) with a locking compartment
- Bigger oilpan bash plate and centerstand bash plate
- Plastic front fairing for the lower engine (the 'bra') mounted to the crash bars
- Dash board with the speedometer and control lights of the previous version and small tachometer and clock
- Solo seat with "solo rack" that stayed on the subframe when the solo seat was removed
- Frame-mounted 1/2 fairing with rectangular headlight, windshield and turn signals
When the solo rack is retrofitted, the seat latch plate (with passenger grab handle) is removed from the subframe and installed on the front of the solo rack. PDs which shipped with the solo seat (not all did) had latch plates without a grab handle.
1991-on GS and PD
In 1991 the GS got the PD-style fairing, shaped differently to match the steel tank. The dashboard is altered for both models, now having a large speedometer and tachometer. The clock is available as an accessory that bolts onto the handlebar clamps (and looks terrible). The other major change is the switchgear; these bikes now have the pushbutton switches that were introduced on the K series. Other changes:
- Completely revised wiring harness.
- Floating front brake rotor.
- Stainless muffler (with separate brackets) replaces the original chromed steel one.
- Revised bash plate with a redesigned oil pan having the drain in the rear wall.
- Adjustable windshield.
- Standard accessory socket.
- Revised steering head bearing system (also from the K series) and fork caps (no more turn signal stalks).
- Revised fender brace with additional holes for mounting the low fender. The low fender itself also changed.
- '92-on PD models are called (and marked) PD instead of Paris-Dakar. Only '90 and '91 models actually say Paris-Dakar.
- Euro models got the flush gas cap, which the US models always had.
Fork/fender braces
The '88-90 bikes came with a simple curved brace 31 42 1 452 517 with four holes for mounting to the fork leg tabs. At first there was only a high fender, and for customers who wanted it mounted low there was a US-built brace which allowed this. In 1989 a low fender was offered, which attached to studs that were used in place of the regular bolts.
When the GS was updated in 1991, a new 8-hole brace 31 42 2 312 119 appeared. This spread out the mounting points for the fender, propably to reduce the paint cracking that had been common. The fender, of course, had holes that were spaced farther apart for this. The brake hose holder was also changed.
Gearing and speedometers
In general the 800cc models came with a 3.20 final drive ratio, and the 1000cc models had a 3.09. Those were the only gear ratios produced for the Paralever Airhead models. The earlier G/S had a 3.36. Different final drive ratios required different speedometer gearing, and often the faces were marked with different shift points.
All speedometers are marked with a W number (Wegdrehzahl, literally "path turning count" but more practically the speedometer ratio or coefficient), which represents the number of turns of the cable needed to accrue one mile or kilometer. The W roughly corresponds with the final drive ratio, although this is not mathematically consistent across all bikes. For each of the speedometers listed below, the intended FD ratio and the W are given.
We'll start with the G/S speedometers, just for perspective and because they are physically interchangeable. In compliance with US law, the '81 and '82 G/S speedometers for the USA had the required 85MPH max and the emphasis on 55MPH.
- KPH 3.36, 62 12 1 244 652, W0773? G/S
MPH 3.36, 62 12 1 244 036, 85MPH version(obs)- MPH 3.36, 62 12 1 244 653, W1244 G/S
- KPH 3.44, 62 12 1 244 651, W0793 R65GS
'88-90 GS speedometers were physically similar but had a larger housing and also were produced with lower W to match the taller final drives.
- KPH 3.09, 62 12 1 244 644, W0737
- MPH 3.09, 62 12 1 244 645, W1186
- KPH 3.20, 62 12 1 244 646, W0747?
- MPH 3.20, 62 12 1 244 647, W1202
With the dashboard redesign in 1991, mounting posts were added to the back of the speedometer. Although the final drive ratios did not change, the W were adjusted downward slightly.
- KPH 3.09, 62 12 1 244 703, W0715
- MPH 3.09, 62 12 1 244 704, W1144
- KPH 3.20, 62 12 1 244 701, W0735
- MPH 3.20, 62 12 1 244 702, W1190
For reference, the Roadster kept the same W as the GS but the cable angle was different so they have different part numbers. It may be possible to install one of these in a GS if neeeded. None of these are still available new.
- KPH 3.09, 62 12 1 244 771, W0715
- MPH 3.09, 62 12 1 244 772, W1148
- KPH 3.20, 62 12 1 244 774, W0735
- MPH 3.20, 62 12 1 244 767, W1190
GS Sources:
Replacement Valeo starters: (also read the rebuilding article)
Bob Spencer
Ace Houston Warehouse
1-800-392-3332
Their part# 432586, was D6RA15
Replacement fork parts:
Forking by Frank:
Frank's Maintenance and Engineering, Inc.
Phone: (847) 475-1003
https://franksforks.com
