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Content of improvements

This improvement in addition to the crank case bearing fixation should enhance balance drive durability significantly.

The teeth width of the starter gear (part no. 434 844) has been increased by around 50% and the teeth width of the balance gear (part no. 365 749) by around 20% (see Figure 1: Increased teeth width). Through this, Rotax have been able to achieve a high quality and smoothed tooth surface.


IMPORTANT: Starter gear (part no. 434 844) is only compatible with balance gear (part no. 635 749). Make sure you exchange the improved balance and starter gear pairwise!

Engines will be equipped with the improved parts as of engine serial number 8643405 and are available as spare parts.

Installation of Balance drive

Install the balance drive as described in the Repair Manual 125 MAX DD2 evo in sections “Installation of balance gear” and “Installation of starter gear”.  Due to corrosion protection it is necessary to completely degrease the three M6 threads (see Figure 2: M6 threads) inside the starter gear using an appropriate cleaning agent (e.g. brake cleaner). This is required to ensure a proper hardening of the Loctite to fix the clutch to the starter gear. ROTAX will not accept any warranty claims for failures caused by non-degreased starter gear threads.