912iS Clutch maintenance

Rotax changed the design of the clutch housing. 

All 912iS engines are equipped with a clutch featuring lead drain holes. The clutch inspection interval is set at 1000 hours. This same rule applies if you have a 912UL (ULS) with the updated clutch.

Regarding the 912UL (912ULS), if the overload clutch part number 996886 (without lead drain holes) is installed and the use of leaded fuel constitutes more than 30% of the engine's operation, the inspection interval is reduced to 600 hours.

Engines of the following types and serial numbers, equipped with overload clutch without drain holes, fall under this category: 912 A up to S/N 4410612 inclusive, 912 F up to S/N 4412860 inclusive, 912 S up to S/N 4922983 inclusive, 912 UL up to S/N 4405961 inclusive, 912 ULS up to S/N 9574657 inclusive. Kindly review your Maintenance Logs to confirm whether the overload clutch has been replaced during maintenance, service, or overhaul.

It is an interesting topic and one that I can definitely disagree on with the factory.  The time limit is expressed in hours only due to the fact that the iS engine overload clutch has a zero degree free-play which eliminates the possibility to check wear by a friction test.  (see MML for a 912 ULS equipped with 30 degree dogs) 

The best way to determine if you are in need of service with your gearbox is rather subjective but effective.  If you warm up your engine to operating oil temperature and then drop down to your idle speed....LISTEN to the gearbox. If the engine has rattle or banging in the gearbox and you must advance the throttle above idle to stop it then it is time to remove it and have a reshim.  This will save you very expensive repairs later.  The worst thing you can do with a gearbox equipped Rotax is allow it to trash itself while you insist on waiting for the time to come up on the hobbs meter.   Please don't wait for that, the repair bill will eat you up.  On average this starts to be a issue about 400 hours from what I see. I am also considering 1600 as low RPM. 

Cheers

I fully agree with RW. He knows his stuff. ?