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This post takes you through the steps to change the front sprocket of your Rotax Max 125 engine and how to remove and re-install your clutch drum.

Once you notice that your front sprocket is worn, it's a good idea to change your front and rear sprocket and chain at the same time, as they will usually wear at the same rate.

Tools required for this job are:

Torque wrench able to do 110Nm (optional)
Breaker bar
16mm or 17mm ring spanner
5mm allen key
38mm impact socket
17mm impact socket (optional)
5mm in-hex socket (optional)
Rotax sprocket holder & locking tool for ring gear


Step 1 - Remove the clutch cover by undoing the 3 M6 cap screws, loosening the cover.

Step 2 - Insert the Rotax locking tool into the ring gear to lock it in place.

Step 3 - Remove clutch retaining nut and washer.

Step 4 - Remove clutch drum from engine.

Step 5 - Put the clutch drum into the sprocket holding tool and use the 38mm socket to remove the sprocket retaining nut from the drum.

Step 6 - Remove front sprocket dowel pin from clutch drum and insert the new sprocket into the clutch drum (don't forget to re-insert the dowel pin). Use Loctite on thread to retain nut on sprocket.

Step 7 - Insert sprocket into sprocket holding tool and tighten the nut to 110Nm. 

Re-installation is the reverse process of the above steps.

Firstly, install the thrust washer, o-ring, bearing, then the clutch shoe, retaining washer and finally retaining nut (don't forget to use some Lactate on the retaining nut).

Lastly, re-install the clutch cover and you're all done...

Follow this link to purchase any of the required parts for this job or if you have any questions, please leave a comment or send an enquiry here.



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