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Trouble starting a 912 ULS

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johnelling

Joined: 23 Feb 2013
Posts: 18

Posted: Fri Aug 02, 2013 8:00 am Post subject: Trouble starting a 912 ULS

Folks,



I've gradually had trouble starting a ULS with the 912 Rotax high torque 

starter.  First it did not like starting when it was cold. Then the 

sprag seemed to come disengaged without turning the engine over enough 

to start.  Finally I started getting a gear-grinding noise.  Then 

eventually the gears never engaged; just a grinding noise.



I checked the starter alignment between the two ears for the bolts. 

Perhaps a 0.010" difference between the gaps of the two ears and no way 

to adjust that I could see since the ears of the starter flange are 

threaded as are the bolt holes on the engine.



I removed the Rotax starter and found the gear surface was a little 

rough as was the mating gear teeth inside the engine.  Probably from the 

grinding...  I replaced the starter with a Skytec, aligned as best I 

could to exactly the same position as the Rotax starter (off about 

0.010" between the top and bottom ears of the starter flange and the 

engine surface).  The Skytec starter does exactly the same thing - 

grinds the gears without really engaging.



Anyone have any ideas?  Anything I should check before I start taking 

apart the engine to get to the starter gears and clutch?



John

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johnelling

Joined: 23 Feb 2013
Posts: 18

Posted: Fri Aug 02, 2013 9:08 am Post subject: Trouble starting a 912 ULS

Folks,



One more data point on the trouble starting:  It is not the battery 

current.  I've connected a truck battery in parallel with the plane's 

battery (so the ignition is switching more amps) and not solved the problem.



John

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ptag.dev(at)tiscali.co.uk
Guest

Posted: Fri Aug 02, 2013 1:43 pm Post subject: Trouble starting a 912 ULS

Hi! John,

Where is your battery situated ? How far from the starter ?  I had untold

problems with the Jabiru 3300 six cylinder until I put two Odessey 13Ah

batteries in parallel within 18" of the starter and used welding cables for

the leads.

Bingo not so much as a problem since.

Regards

Bob Harrison G-PTAG Europa now with 914 Rotax.



--

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BARRY CHECK 6

Joined: 15 Mar 2011
Posts: 738

Posted: Sat Aug 03, 2013 2:30 am Post subject: Trouble starting a 912 ULS

John:



1 - What does the gear engagement points look like?  If the gears are too new to show ware take some blue Dykem and coat the ring gear teeth and the starter gear teeth.  Then try starting.  You will have wear marks showing the gear contact - If they are not straight and even from face to face you have an alignment issue.

 



2 - If the gears are not engaging - Could the mounting system be totally incorrect?  Am I to assume at one point and for a long time there were NO starting issues?  If so...  What changed?

 



3 - Any hard landings?  

 

Barry

On Fri, Aug 2, 2013 at 12:00 PM, John Elling <jelling(at)newmexico.com (jelling(at)newmexico.com)> wrote:

 [quote]--> RotaxEngines-List message posted by: John Elling <jelling(at)newmexico.com (jelling(at)newmexico.com)>

  

 Folks,

 

 I've gradually had trouble starting a ULS with the 912 Rotax high torque starter.  First it did not like starting when it was cold. Then the sprag seemed to come disengaged without turning the engine over enough to start.  Finally I started getting a gear-grinding noise.  Then eventually the gears never engaged; just a grinding noise.

  

 I checked the starter alignment between the two ears for the bolts. Perhaps a 0.010" difference between the gaps of the two ears and no way to adjust that I could see since the ears of the starter flange are threaded as are the bolt holes on the engine.

  

 I removed the Rotax starter and found the gear surface was a little rough as was the mating gear teeth inside the engine.  Probably from the grinding...  I replaced the starter with a Skytec, aligned as best I could to exactly the same position as the Rotax starter (off about 0.010" between the top and bottom ears of the starter flange and the engine surface).  The Skytec starter does exactly the same thing - grinds the gears without really engaging.

  

 Anyone have any ideas?  Anything I should check before I start taking apart the engine to get to the starter gears and clutch?

 

 John

 

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Roger Lee

Joined: 10 Jan 2006
Posts: 1464
Location: Tucson, Az.

Posted: Sat Aug 03, 2013 3:27 pm Post subject: Re: Trouble starting a 912 ULS

It sounds like you may have lost your sprag clutch that engages the engine with the starter then releases as soon as the engine speeds past the starter rpm.

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