Hard starting Rotax 912 ULS

The "repair" seems to be good. This past Sunday I went out to fly. Again, it started right up. Warmed it up then gassed it up. Just did a couple flights in the pattern because it was a bit windy(16 gusting to 24) but the plane handled well and no problems with the engine. Looking forward to more flying.

Charles Clayton wrote:

The carbs were rebuilt at Lockwood 4 years ago. At that time they had to replace the floats. That's the last time my A&P synced them. Going forward I'm going to have him do it every annual. It's a Sensenich prop. I usually use choke when I start it throttle all the way out. I change the plugs at every annual which would have been last May. I plan to put new plugs in now regardless of what else has to be done. The prop continues to turn but when it tries to start it sometimes stops.

Per the MML, the carbs must be resynched every 100 hours, or annually, whichever comes first.  They also need to be inspected (which means taking them off and opening them up) every 200 hours.

Also, as you discovered, you should have your throttle closed when using your choke.

So my "joy" was short lived. After my mechanic and I worked on it, it started right up. Except for one time and I thought that was because I had kind of killed the battery. So I decided to replace the battery with an Earth X. After that I had no trouble starting it up, made a couple of flights and no issues. So yesterday I went out to fly with my daughter and guess what. No go. This time however, the prop kept stopping. I maybe got 2 complete revolutions then it would stop and I hear something like a gear spinning and then the prop would catch again. If I'd turn the key I wasn't getting even a full revolution before it would stop again. Gearbox issue?

This sounds to me like a problem with the Bendix drive in the starter motor.  Either that, or an intermittent wiring issue in the starter circuit.

Sounds very much like the "Sprag Clutch".

Sprag clutches are very susceptible to accelerated wear when the pilot persists with a weak battery (sound familiar?)