Could you put a 912iS gearbox on a 912ULS?

Roger Lee
LSRM-A & Rotax Instructor & Rotax IRC
Tucson, AZ Ryan Airfield (KRYN)
520-349-7056 Cell

  • Re: Gearbox question

    by » one month ago

    Hi Roger

    Yes you can however it requires the gearset also.  The only difference between the current production of the ULS and the iS Sport is the fact that the iS has a zero clearance dog gear.  This is so the 2 crankshaft sensors can get a clean signal from them in the startup of the engine.  Both have an overload clutch now and both (since 2018) have the oil spray in the housing.  

    The drawback to the iS gearbox with zero clearance however is the test for friction torque setting is not longer there with zero degree freeplay.  You are then relying on the MML manual to tell you at what hours you should take it off for setting the shims.  As I have said before the MML sets an extremely long time period that is excessive in my view.  The only sure way to reshim it at the correct time is to listing to the backlash.  If the shims are not correct the engine will be very rough at idle, whatever idle they are using.  If it is for personal use you should get up to 600 hours but in training use normally 450 from what I have seen.  This is because the cycles of training, idle to high speed, are increased significantly.  The more time at idle speed, the more starts and stops, the more the wear in the gearbox.  

    So yup, they can be used on a ULS however I would not follow the iS manual of waiting to 1000 hours for maintenance.  That is an excessive number in my view.  Remember you lose the ability to check the wear as we did with the 30 degree freeplay in the ULS engine fitted with a clutch. 


    38698_2_iS gearbox hours.jpg (You do not have access to download this file.)

    Thank you said by: RotaxOwner Admin

You do not have permissions to reply to this topic.