One idea at a time in focus mode
Haynes clutch stacks for each engine, and one aftermarket kit listing with no capacity figure.
Before you start
Your own risk. Wrong jetting or timing can seize the engine. This is information, not advice.
How many steps: 2
Step 1 of 2
The 122 and the 123 do not share a clutch pack.
Haynes: Type 122 has 6 friction plates and 6 plain plates. Friction service limit 2.8 mm. Plain-plate distortion max 0.15 mm. Spring free length service limit 31.6 mm. Type 123 has 6 friction plates and 5 plain plates. Friction standard 3.0 mm. Plain standard 1.0 mm. Pack service limit 21.2 mm. Spring free length service limit 34.2 mm. The centre nut at 80 Nm is the 123 only. Hartrusion adds that the 123 basket is bolted to the input shaft and the 122 basket sits on it, and that the shaft diameters differ. A kit sold for both engines still has to match the basket in front of you.
Step 2 of 2
A heavier kit is sold. Whether you need it is open.
One UK listing sells a clutch kit for Rotax 122 and 123 with friction plates, steel plates and heavier springs, and says it is meant to cope with a larger carb or a different exhaust. It does not give a torque capacity or a dyno result. Whether a particular bike needs it is To verify. Gearbox oil in Haynes is SAE 75W-90, API GL-4 or higher, about 850 cc, drain plug 24 Nm. That grade stays the stock fill. A claim that a different oil stops a clutch dragging, beyond that grade, is To verify.
This guide is done. Your place stays on this device.
Haynes: Type 122 has 6 friction plates and 6 plain plates. Friction service limit 2.8 mm. Plain-plate distortion max 0.15 mm. Spring free length service limit 31.6 mm. Type 123 has 6 friction plates and 5 plain plates. Friction standard 3.0 mm. Plain standard 1.0 mm. Pack service limit 21.2 mm. Spring free length service limit 34.2 mm. The centre nut at 80 Nm is the 123 only.
Hartrusion adds that the 123 basket is bolted to the input shaft and the 122 basket sits on it, and that the shaft diameters differ. A kit sold for both engines still has to match the basket in front of you.
Source: Haynes manual 4298, and Hartrusion’s engine-differences page
One UK listing sells a clutch kit for Rotax 122 and 123 with friction plates, steel plates and heavier springs, and says it is meant to cope with a larger carb or a different exhaust. It does not give a torque capacity or a dyno result. Whether a particular bike needs it is To verify.
Gearbox oil in Haynes is SAE 75W-90, API GL-4 or higher, about 850 cc, drain plug 24 Nm. That grade stays the stock fill. A claim that a different oil stops a clutch dragging, beyond that grade, is To verify.
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