When should an Airhead gearbox be opened?
Abnormal noise, shifting problems, oil leakage or known internal damage are reasons for inspection, but symptoms alone do not identify the failed part. The gearbox must be assessed as an assembly. Bearings, shafts, gears, shift components and housing condition determine the repair scope after disassembly and measurement.
What does a longer gear change?
A taller ratio can reduce engine speed at the same road speed in that gear. Whether it is pleasant depends on the engine's torque, final-drive ratio, wheel circumference and the load carried. A change to one gear does not turn a motorcycle into a different complete drivetrain.
When might a shorter gear be useful?
A shorter ratio changes the relationship between engine speed and road speed and may suit a particular low-speed or sporting brief. The trade-off has to be considered with the other gears and final drive. Choosing a gear from a forum recommendation without identifying the actual gearbox can produce the wrong result.
What does Diamond Atelier offer?
We rebuild BMW two-valve boxer gearboxes and can specify longer or shorter gear ratios. We first review the gearbox generation, its condition and the rider's use. The selected parts, compatibility and final work are defined for that specific motorcycle. See the gearbox service.
What should the enquiry include?
Send the model and year, any known gearbox number or previous work, symptoms, rear-drive ratio if known, tyre size and the riding goal. A clear description of what you want to improve is more useful than requesting a particular gear pair without context. Discuss a gearbox project.
Further reading
Owners ask about a longer fifth after a gearbox failure and long fifth versus short first. Those are individual cases, not universal specifications.