Martin,
Remember all the posts, SBs, SLs, Sis on =93Genuine Rotax Parts=94 kept com
ing 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 ou
t of its ears.
The Sky-tec has the same nose seal as the Rotax. The problem with =93Joe B
ag of Doughnuts=94 installer is they fail to note the spacers and O rings t
hat 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=92ve had to straight
en them and fab a new spacer to suit my liking to get the gear length exact
ly the length of the other starter, which was a waste of time. Simply rein
stall 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/electri
cal routings with cold fingers getting it all back into place without pulli
ng apart. The O rings help but I find using safety wire to hold the starte
r nose and tail tight while installing prevents the starters from falling a
part 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 t
he .020 safety wire off, and push it home.
I normally do starter changes and engine rubber mount changes at the same t
ime by pulling the engine on a 5 year. If you make the engine easy to disc
onnect and come off like a pod, it is a 4 hour hose, rubber, starter cleanu
p, and service rather than days of frustration.
Best Regards,
Bud Yerly
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s 10
From: Martin Tuck<mailto:MJKTuck@cs.com>
Sent: Wednesday, December 2, 2020 11:09 PM
Subject: Re: Europa-List: Rotax 912ULS starter motor
Nine years ago on the Rotax Owners Forum there was some commentary surround
ing the suitability of the Sky-Tec starter due to the lack of oil seal resu
lting in oil in the starter and possibly compromising the oil return system
.
This is explained in a Rotax service bulletin.
See Rotax Service Letter=EF=BDSL-912-014 / 914-012 / 2ST-008<https://eur
05.safelinks.protection.outlook.com/?url=http%3A%2F%2Flegacy.rotax-owner.
com%2Fsi_tb_info%2Fserviceletter%2Fsl-912-014-r3.pdf&data=04%7C01%7C%7Ce4
413423f0a147ea925a08d897413630%7C84df9e7fe9f640afb435aaaaaaaaaaaa%7C1%7C0%7
C637425653619573178%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2l
uMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C1000&sdata=7JH9LR5coDY%2FiHPA1jXP%2
FaAdctWtKMibkk4lAEeCbYY%3D&reserved=0>=EF=BDfor 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 starte
r.
I=EF=BDve tried them both.=EF=BD The Rotax high torque is what I inst
alled ($1100USD), mainly because my plane was kept stock as much as possibl
e.=EF=BD For the Experimenter I recommend the Sky-Tec as it costs half (
<$500 USD) as much and is quite torquey.=EF=BD
=EF=BD
Both spin the prop with authority, easily surpasses the ignition excitation
speed.=EF=BD With plugs in and ignition off, I see 500 RPM for a 914/91
2 and 400-450 for a 912S/iS.=EF=BD
Even with a slightly low battery, starts are crisp.=EF=BD This lengthens
the life of the sprag clutch.=EF=BD But these clutches do wear and some
where within 1000 hours even on a well maintained 912S engine with good sta
rting, it may fail.
=EF=BD
In my Rotax troubleshooting update in March, I went into the soft start/sta
rting ignition problems of the Rotax.=EF=BD As many have learned, once t
he starter can=EF=BDt push past the compression peak at ignition, the en
gine will kick back which will quickly wear the sprag clutch.=EF=BD What
I didn=EF=BDt explain completely was when the sprag clutch begins to we
aken and slightly slip, this will exacerbate the kickback issues.=EF=BD
Adding a high torque starter on a defective clutch will not be the total an
swer to the kickback.=EF=BD 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 th
e clutch to slip so it no longer is an effective one way clutch.=EF=BD T
he good news is there is no damage to the starter or the crank shaft when t
his happens unless the engine continues to have =EF=BDkick backs=EF
=BD with the defective clutch, then things break and fowl the engine with m
etal 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 wa
y clutches.
=EF=BD
I recommend that if you have an XS firewall forward (with the ring mount) t
he high torque starter will fit.=EF=BD (Note the Rotax high torque may c
ome with the tabs still attached which must be cut/ground off.=EF=BD Our
dealers in the States supply them ready to install without the tabs.)=EF
=BD I found the Sky-Tek to be well built and spun up quickly on some lig
ht sport aircraft we have around here.=EF=BD I think it is good insuranc
e for preserving the sprag clutch. =EF=BD=EF=BDThe Sky-Tek is cheaper
also.
=EF=BD
For those with the Classic FWF, I=EF=BDm afraid neither of the high torq
ue starter options will fit the original Classic mount.=EF=BD It is too
long by only a few millimeters, but it is too long.=EF=BD Service your s
tarter for good operation, keep the battery up, and on very cold starts, us
e engine preheat.
=EF=BD
Best Regards,
Bud Yerly
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m/?url=http%3A%2F%2Fwww.customflightcreations.com%2F&data=04%7C01%7C%7C
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=EF=BD
From: arwel pritchard<mailto:arwel.pritchard@powercom.ltd.uk>
Sent: Tuesday, December 1, 2020 8:51 AM
Subject: Europa-List: Rotax 912ULS starter motor
=EF=BD
Good morning
=EF=BD
Has anybody replaced the starter motor on a 912ULS with a Sky-Tec model. Ap
parently, it cranks the engine faster than the standard Rotax model.
I have been quoted =EF=BD660 for this unit, seems quite expensive, but i
f it preserves the sprag clutch (which I had to replace last year at much m
ore cost) its got to be a good thing?
Just wondering if it=EF=BDs worth it.
=EF=BD
=EF=BD
=EF=BD
=EF=BD
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