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hard Starting Rotax 912ULS

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JohnF

Joined: 13 May 2010
Posts: 124

Posted: Sun Oct 01, 2017 7:10 pm Post subject: hard Starting Rotax 912ULS

Rotax normally started on first or second blade over. Since last annual where new plugs were installed starting takes several tries.



Battery is on a tender and strong. Fuel pressure normal. OAT mild.

After starting ( typically on 3rd try) engine runs just fine.



Correct plugs, correct gap, fresh fuel.



Suggestions?

dpark748(at)me.com
Guest

Posted: Sun Oct 01, 2017 11:58 pm Post subject: hard Starting Rotax 912ULS

Correct leads?

Dave Park



Sent from my iPad



 	  Quote: 	
		   On 2 Oct 2017, at 04:10, JohnF <n29cx(at)ridgeviewtel.us> wrote:

 

 

 

 Rotax normally started on first or second blade over. Since last annual where new plugs were installed starting takes several tries.

 

 Battery is on a tender and strong. Fuel pressure normal. OAT mild.

 After starting ( typically on 3rd try) engine runs just fine.

 

 Correct plugs, correct gap, fresh fuel.

 

 Suggestions?

 

 

 

 

 Read this topic online here:

 

 http://forums.matronics.com/viewtopic.php?p=473258#473258

JohnF

Joined: 13 May 2010
Posts: 124

Posted: Wed Oct 04, 2017 8:04 am Post subject: Re: hard Starting Rotax 912ULS

After a lot of thought about hard starting, I took a hint from another RV-12 pilot and ran the engine on the ground at 4,000 RPM for about 4 minutes, in the hope that oil fouling of the plugs might be involved, and that the high RPM run might help clear things up. This is because I typically have to taxi about 3/4 mile after landing to my hangar which might possibly cause oil fouling.



This morning it was fairly chilly so I put on the engine heater (space heater ducted into the engine cowl) for about 40 minutes. 



Upon starting, the engine fired up on the first blade over, just as in the past.



I am going to make it a practice to run the engine at fairly high RPM for a few minutes just prior to shut down when back at the hangar and see if I get consistent results.



Thanks for you input.

DHeal

Joined: 15 Feb 2017
Posts: 3

Posted: Wed Oct 04, 2017 8:40 am Post subject: Re: hard Starting Rotax 912ULS

Be sure that your spark plugs are appropriately gapped (.023 in winter and .027 in summer -- I use 0.025 year-round here in moderate Northern California).  Be sure that your throttle is fully closed for the first cold start of the day and the "choke" is at least partially "on".  The instant the engine fires, ease in a bit of throttle and then gradually remove the choke.  



Alternatively, apply "full choke and fully closed throttle" and crank the engine over for a few revs with the ignition "off" and then stop.  Then turn the choke off, crack the throttle, turn the ignition "on", and start the engine.



In over 550 hours of my RV-12's operation the aforementioned standard ROTAX operating procedure has worked well.  We have extensive taxiing and ground idle operations here at our controlled airport and I do not think that this negatively influences subsequent starting of the engine.  IMHO, the "4,000 rpm for 4 minutes" is likely a waste of your time and results in unnecessary wear on your engine.

JohnF

Joined: 13 May 2010
Posts: 124

Posted: Wed Oct 04, 2017 9:20 am Post subject: Re: hard Starting Rotax 912ULS

Thanks, DHeal..... I will try your starting technique and see how that works. I like it better than the high speed run I tried.



I always gap plugs to .025 year in and out as you do. New plugs every annual because they are so inexpensive.



325 hours on the plane and this odd starting thing just came up...again, thanks.

johnelling

Joined: 23 Feb 2013
Posts: 18

Posted: Sat Oct 07, 2017 12:09 pm Post subject: hard Starting Rotax 912ULS

I had a similar-sounding problem with my Rotax 912ULS.Â  It turned out to 

be the sprag clutch. When the problem began, the engine started better 

when warm but would not start when cold.Â  When I finally changed it out, 

I found metal in it.

bob(at)fly-ul.com
Guest

Posted: Mon Oct 09, 2017 6:56 am Post subject: hard Starting Rotax 912ULS

On 01:08 PM 10/7/2017, John Elling wrote:



 	  Quote: 	
		  I had a similar-sounding problem with my Rotax 912ULS.Â  It turned out to be the sprag clutch. When the problem began, the engine started better when warm but would not start when cold.Â  When I finally changed it out, I found metal in it.


	


What was the problem? Was the engine not turning over fast enough?

JohnF

Joined: 13 May 2010
Posts: 124

Posted: Tue Oct 10, 2017 8:52 am Post subject: Re: hard Starting Rotax 912ULS

I flew this morning...25-degrees F, and used the hint given me above, and the engine fired on the first blade over. Perfect. thanks a lot...will continue using this procedure.

Duncan McFadyean

Joined: 18 Jan 2011
Posts: 219

Posted: Wed Oct 11, 2017 2:38 am Post subject: hard Starting Rotax 912ULS

John,

Would you confirm please which of the various offered procedures ("above") you found successful?

Rgds.,

Duncan.

 

 

 	  Quote: 	
		   ----Original Message----

From: n29cx(at)ridgeviewtel.us

Date: 10/10/2017 17:52

To: <rotaxengines-list(at)matronics.com>

Subj: RotaxEngines-List: Re: hard Starting Rotax 912ULS



--> RotaxEngines-List message posted by: "JohnF" <n29cx(at)ridgeviewtel.us>



I flew this morning...25-degrees F, and used the hint given me above, and the engine fired on the first blade over. Perfect. thanks a lot...will continue using this procedure.





Read this topic online here:



http://forums.matronics.com/viewtopic.php?p=473441#473441



<b             - sp;          - NEW MATRONICS Lnbsp;                      -Matt Dralle, List============

JohnF

Joined: 13 May 2010
Posts: 124

Posted: Wed Oct 11, 2017 11:13 am Post subject: Re: hard Starting Rotax 912ULS

The hint that seemed to work well was in the first paragraph of DHeal's post.



John

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