Does this sound like a sprag clutch problem?

by Jason Savill in 912 / 914 Technical Questions 9 years ago

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Re: Does this sound like a sprag clutch problem?

by Jacques Van der Westhuizen » 9 years ago

Jacques Van der Westhuizen

2 6 0

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

Thank you said by: Jason Savill

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Re: Does this sound like a sprag clutch problem?

by Rhett Mitchell » 9 years ago

Rhett Mitchell

8 99 0

To add to that, a "soft starter" may help too, if not already installed.
Battery Wiring size should be 16mm2. Manufacturers put in smaller but in the installation manual (I think) it says 16mm2 minimum. High count, multi strand wire is good.
If battery is behind seats or further back larger wire may be required.
Good, clean connections and earths.
The faster it spins, the easier it starts.
Replaced my original 10mm2 (industrial wire) with 16mm2 multi and made a world of difference.

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Re: Does this sound like a sprag clutch problem?

by Jason Savill » 9 years ago

Jason Savill

1 8 0

Hi Gents,
The owner removed the engine and had a new sprag clutch fitted.The engine is now starting perfectly.

Thank you all for your feed back :)

Jason

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Re: Does this sound like a sprag clutch problem?

by Norvel Swallie » 3 years ago

Norvel Swallie

23 37 73

I am having a similar problems. Did the Sprag Clutch solve the problem?

Ernie

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Re: Does this sound like a sprag clutch problem?

by James N Parker » 3 years ago

James N Parker

1 75 347

Norvel Swallie wrote:

I am having a similar problems. Did the Sprag Clutch solve the problem?

Ernie

The thread you appended to was last updated six years ago. At that time, the OP said his engine is starting perfectly after replacing the sprag clutch. Since the OP has not returned to ask for further assistance in solving the problem, I think it's almost certain that the sprag clutch replacement did resolve the issue.

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Does this sound like a sprag clutch problem?

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