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Rotax 912ULS starter motor

 
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MJKTuck(at)cs.com
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PostPosted: Sat Feb 06, 2021 1:07 pm    Post subject: Rotax 912ULS starter motor Reply with quote

Hi all,

Closer scrutiny of the SkyTec starter shows eligibility for the Rotax 912ULS Serials 4425001 and on.

I have an older 912UL. Do you know if there a similar hi-torque starter available for it?

Anyone have experience installing the SkyTec starter on the 912UL?

Regards,
Martin Tuck

On 12/3/2020 6:47 AM, Bud Yerly wrote:

Quote:
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Martin,
Remember all the posts, SBs, SLs, Sis on �Genuine Rotax Parts� kept coming on and on?
I normally use Rotax parts on my engine because I can afford it and I plan on selling my aircraft when I get old.�� My plane and I are aging similarly by the way.� But my plane is easier to touch up and is not growing hair out of its ears.

The Sky-tec has the same nose seal as the Rotax.� The problem with �Joe Bag of Doughnuts� installer is they fail to note the spacers and O rings that go on the spindly threaded rods.� Sky-tec threaded rods are not as hard a steel as the Rotax and bend usually in shipment.� I�ve had to straighten them and fab a new spacer to suit my liking to get the gear length exactly the length of the other starter, which was a waste of time.� Simply reinstall the existing spacers and the clamp and it works just fine.

The Rotax heavy MX manual shows the spacers, O rings and clamp.� That rear clamp will keep the starter securely fastened preventing the somewhat soft threaded rods from worrying you about a sagging starter.

You just have to work around the ring mount, footwell, and any hose/electrical routings with cold fingers getting it all back into place without pulling apart.� The O rings help but I find using safety wire to hold the starter nose and tail tight while installing prevents the starters from falling apart on install which can damage brushes.� Once the starter starts to slip in place, and you have not forgotten to put the clamp back on, simply cut the .020 safety wire off, and push it home.�

I normally do starter changes and engine rubber mount changes at the same time by pulling the engine on a 5 year.� If you make the engine easy to disconnect and come off like a pod, it is a 4 hour hose, rubber, starter cleanup, and service rather than days of frustration.

Best Regards,
Bud Yerly


Sent from Mail for Windows 10

From: Martin Tuck (MJKTuck(at)cs.com)
Sent: Wednesday, December 2, 2020 11:09 PM
To: europa-list(at)matronics.com (europa-list(at)matronics.com)
Subject: Re: Rotax 912ULS starter motor


Nine years ago on the Rotax Owners Forum there was some commentary surrounding the suitability of the Sky-Tec starter due to the lack of oil seal resulting in oil in the starter and possibly compromising the oil return system.

This is explained in a Rotax service bulletin.
See Rotax Service Letter�SL-912-014 / 914-012 / 2ST-008�for more information.




That was a while ago and put me off the idea of using that starter.

Do you know if the Sky-Tec starter has since been modified to prevent this? It doesn't sound like those who have used it have had issues like this.

Thanks,
Martin Tuck
N152MT
Wichita, Kansas
On 12/1/2020 7:16 PM, Bud Yerly wrote:
Quote:

Arwel,
In my Troubleshooting guide I mention the starter issues.
It is my opinion all Rotax engines should upgrade to the high torque starter.
I�ve tried them both.� The Rotax high torque is what I installed ($1100USD), mainly because my plane was kept stock as much as possible.� For the Experimenter I recommend the Sky-Tec as it costs half (<$500 USD) as much and is quite torquey.�

Both spin the prop with authority, easily surpasses the ignition excitation speed.� With plugs in and ignition off, I see 500 RPM for a 914/912 and 400-450 for a 912S/iS.�
Even with a slightly low battery, starts are crisp.� This lengthens the life of the sprag clutch.� But these clutches do wear and somewhere within 1000 hours even on a well maintained 912S engine with good starting, it may fail.

In my Rotax troubleshooting update in March, I went into the soft start/starting ignition problems of the Rotax.� As many have learned, once the starter can�t push past the compression peak at ignition, the engine will kick back which will quickly wear the sprag clutch.� What I didn�t explain completely was when the sprag clutch begins to weaken and slightly slip, this will exacerbate the kickback issues.� Adding a high torque starter on a defective clutch will not be the total answer to the kickback.� Because the Rotax sprag clutch is a trapped un-round roller type one way clutch, if the spring that holds the un-round roller in place is loaded excessively, the spring stretches which causes the clutch to slip so it no longer is an effective one way clutch.� The good news is there is no damage to the starter or the crank shaft when this happens unless the engine continues to have �kick backs� with the defective clutch, then things break and fowl the engine with metal parts. Which means it goes from a somewhat expensive repair to a very expensive repair. Youtube has videos on the different types of these one way clutches.

I recommend that if you have an XS firewall forward (with the ring mount) the high torque starter will fit.� (Note the Rotax high torque may come with the tabs still attached which must be cut/ground off.� Our dealers in the States supply them ready to install without the tabs.)� I found the Sky-Tek to be well built and spun up quickly on some light sport aircraft we have around here.� I think it is good insurance for preserving the sprag clutch. ��The Sky-Tek is cheaper also.

For those with the Classic FWF, I�m afraid neither of the high torque starter options will fit the original Classic mount.� It is too long by only a few millimeters, but it is too long.� Service your starter for good operation, keep the battery up, and on very cold starts, use engine preheat.

Best Regards,
Bud Yerly
www.customflightcreations.com
Sent from Mail for Windows 10

From: arwel pritchard (arwel.pritchard(at)powercom.ltd.uk)
Sent: Tuesday, December 1, 2020 8:51 AM
To: europa-list(at)matronics.com (europa-list(at)matronics.com)
Subject: Rotax 912ULS starter motor


Good morning

Has anybody replaced the starter motor on a 912ULS with a Sky-Tec model. Apparently, it cranks the engine faster than the standard Rotax model.
I have been quoted �660 for this unit, seems quite expensive, but if it preserves the sprag clutch (which I had to replace last year at much more cost) its got to be a good thing?
Just wondering if it�s worth it.





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