The adjustment of the balance shaft gears on the Rotax 123 is a bit tricky, as the shafts do not have corresponding markings.
To install the balance shaft gears, the piston must be set to TDC and the markings in the gears must point towards each other. Thus the inner marking on the balancer shaft gearwheel points not to the feather key of the crankshaft, but to the tooth on the left side.
