I had exactly the same problem. I installed a new sky tec high torque starter and odessey battery, that increased the engine cranking speed significantly. ( a good start in fixing the problem)
Secondly, the ULS engine is known for failed sprag clutches after 500 hrs because of the old clutch design, the old starter with low torwue, poor batteries that result in slow speed cranking, engine kickbacks, etc.
Now my engine cranks nice but often, as in your video, it is like the clutch slips while the starter is running. This is definately your sprag clutch... I just had to replace mine.
Tips to preserve the sprag clutch longer:
1. Make sure the battery is fully charge and that the crank speed is fast to avoid kickback from the engine (which wears the clutch spring rapidly)
2. Make sure to have a new type starter and not the old black one...
3. Do not turn the prop backwards, as it engages the sprag clutch and damage it
4. Start the engine with no throttle, and slowly open throttle if engine does not start. (Normal choking procedure applies obviously)
5. Before stopping the engine, get the rpms as low as possible to avoid the engine kickback when turning off the mag switch.
Hope this helps
Regards
Jacques
