Higher 5th gear for airhead gearbox
Hi,
I fitted a 5th gear to my R100GS PD output shaft back in December 2007 that gave a 6% higher ratio. Since then the bike has done 100,000 miles (340,000 miles in all) and it continues to function well. It is a simple and straightforward swap once you have dismantled the gearbox.
The gear (part number: 23221242992z) was supplied by S Meyer BMW; S.Meyer GmbH (limited company) - BMW motorcycle spare parts - Homepage
Meyer's in those days also listed a pair of gears, one for the lay-cluster and one for the output shaft that would give a 10% higher ratio. I fitted the 6% one because at the time they only had that in stock and I couldnt wait.
Airhead gearboxes are quite easy to work on, but it is important to remember to get the endfloat on the three shafts shimmed correctly, so as to ensure longevity. Also bear in mind it is worth checking to see if the outputshaft bearing at the clutch end has provision for a circlip to retain the bearing (BMW went through a phase of manufacturing some shafts without a circlip groove, which can cause premature bearing wear). If it dosen't then (as was the case with my shaft) you should make provision for a circlip on the shaft.
Regards to all
Guy
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