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 LetterSL-912-014 / 914-012 / 2ST-008
<http://legacy.rotax-owner.com/si_tb_info/serviceletter/sl-912-014-r3.pdf>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:
>
> Arwel,
>
> In my Troubleshooting guide I mention the starter issues.
>
> It is my opinion all Rotax engines should upgrade to the high torque
> starter.
>
> Ive 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 cant push past the compression peak at ignition, the
> engine will kick back which will quickly wear the sprag clutch. What
> I didnt 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, Im 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 <https://go.microsoft.com/fwlink/?LinkId=550986> for
> Windows 10
>
> *From: *arwel pritchard <mailto:arwel.pritchard@powercom.ltd.uk>
> *Sent: *Tuesday, December 1, 2020 8:51 AM
> *To: *europa-list@matronics.com <mailto:europa-list@matronics.com>
> *Subject: *Europa-List: 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 its worth it.
>
|