Setting Up The 123 Balance Shaft Gears

[Paul]

The balance gears are the same on the 122 and the 123 Rotax Engines, how they are set up is different though.


At the bottom of the engine there is a M8 bolt that most think it is there to drain the crank case, wrong it is there to enable the set up of the balance gears. You need to undo this with a 6mm Allen key



Note there is a copper washer on that bolt



Using a 5mm Allen key push that in the hole where the bolt was, push up and rotate the crankshaft at the same time, there is a notch in the crank and the Allen key will lock the crank in the correct place for setting up the gears.




Now we have the crank locked in the right place you can go ahead and fit the gears. There are notches on the gears I have highlighted them here with yellow paint to take the photo.

Fit the gear on the balance shaft 1st, there is a mark on the balance shaft that needs to line up with the inner notch on the balance gear. Now you can fit the balance gear on the crankshaft, you need align the outer notches of this gear with on the balance shaft, remember this is all done with the crank locked using the Allen key.



You are all done now, just need to fit a new C-clip and refit the M8 Bolt in the crankshaft.