912S back firing problems + ignition timing

Re: 912S back firing problems + ignition timing

by Gregoire michel » 13 years ago

Gregoire michel

0 2 0

Bill,

Are the kickbacks caused by a faulty sprag clutch can damage the crankshaft or other parts and resulting in an in-flight engine out?

I experienced rough kickbacks on start-up. I already had the HD starter and SSM module. I put a new battery and a charger unit that keeps the battery always full charge. I discovered that my engine starts better and make a lot less kickback if I crank it for a couple of revolution and then turn on a magneto. The inertia of the prop helps the engine not to kickback.

Thanks,

Pat

Re: 912S back firing problems + ignition timing

by Roger Lee » 13 years ago

Roger Lee

131 5.38k 5.44k

As the starer spins up the sprag is engaged and as the engine starts it over speeds the starter and the sprag releases. If you have a bad sprag it usually causes hard starts and a poor engagement of the sprag.

All of what Gregoire said will help a start up and keep kickbacks away. Using a light composite prop compared to a long and or nickel edge heavy Warp Drive prop will also help stave off kickbacks. They can also be a result of low gearbox slipper clutch pressure and poor carb setup, sync and throttle position at start up.

---

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

Re: 912S back firing problems + ignition timing

by Guy De Cleyn » 13 years ago

Guy De Cleyn

2 6 0

Also check the earth connection on the engine.
I had a problem on my SoptCruiser.
The connection looked to seem in very good condition but after disassembling cleaning up and re assembling
the engine started a lot better.
Later after installing the soft start system from Rotax, the engine start very smooth now

Best regards,
Guy

Re: 912S back firing problems + ignition timing

by Lars Bertelsen » 12 years ago

Lars Bertelsen

0 1 0

I have the same problem with sprag clutch after 300h. Rotax have made some changes of engeene since 2007, new flywheel, stronger spiral-spring in sprag cluch, soft start module and suggest not to have long startcabel.
Now I make new fiywheel and sprag clutch, soft start modul is mount 2 years ago, but I am a little unhappy about rotax and not thinking it is my fault, I have made a super instalation in the plane and made all handling of engene by my self.