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912UL turning backwards on shutdown

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Dick Maddux

Joined: 24 Jun 2008
Posts: 516
Location: Milton, Fl

Posted: Sun May 30, 2010 3:54 am Post subject: 912UL turning backwards on shutdown

Well, my old nemesis is back with a vengeance! Yesterday was a very hot (96degree) , muggy,lousy,typical Florida summer day. So why not go fly. I did and after shutting my engine down it slung itself backwards at least 5-10 engine revolutions (not blades) If I would have turned the mags back on, and the jugs didn't blow I betI I could have backed into my parking spot! Everyone that saw this was amazed. They have never seen an engine do this. It has done this too me before about 5 times but never turned backwards that many revolutions.

  Now I do realize that I am the ONLY person in the world that has had this problem (verified by calls to tech reps at Lockwood and LEAF) but I would like this to stop. It's beginning to give me the RA (red ass)

  I only mention this again on this forum to see if some of you gurus agree with me on the procedure I will follow from here. I plan on getting an oil sample today and sending it off for analysis for metal to see if there is any cam damage from collapsed lifters. As I understand it turning the engine backwards could ingest air into the lifters thus causing one or more to collapse thus causing scuffing of the cam lobes (ie:metal) 

  I have performed the valve lifter check after each of these events and at no time in the past have the clearances been greater than 20 thousands which according to the bulletin would indicate air in the lifters. The oil filter has always been free of metal also.

  After this last event at an outlying field, I restarted the engine, the oil pressure fluctuated a little bit at idle (as it always does since I have had the airplane) normal rpm produced steady oil pressure so I flew the aircraft back home (10 minutes) Today I might do another check for air in the lifters but I am sure if any was there, it is gone due to the 10-15 minutes of flight time home.

  I believe  the major causes of this problem are, old premium fuel (over30 days as I was on vacation) high outside temps and the fixed engine ignition timing is off somewhat. I had added octane booster to the fuel as this has helped in the past but probably not added enough.

  I have borescopped the engine cylinders and they seem relatively free of carbon (250 hrstt engine)

   Any ideas?

  I am running a Warp drive prop. I have even thought of going back to the Kiev prop. It is about a pound lighter than the Warp. It,s momentum would be less than the Warp. Maybe that would do it. Mystery!

                                    Thanks,

                                               Dick Maddux

                                               Kitfox 4

                                               Milton,Fl

dave

Joined: 22 Sep 2006
Posts: 1382

Posted: Sun May 30, 2010 4:38 am Post subject: Re: 912UL turning backwards on shutdown

Dick,

 

Are you using avgas or auto  premium ?

 

Sounds like pre ignition-- since you likely do not have a mixture cut off try shutting off the fuel valve at shut down.

 

912 UL will run fine on auto regular  87 grade --with or without ethanol. 

Actually you might want to run a tank of ethanol regular gas through it and see if that helps.

Although many armchair captains will say bal bla bla about ethanol  Rotax does in fact recommend the use of it up to 10%. 

 

Also who says that premium is always premium gas  at the pumps. I VERY rarely use premium if ever on Rotax 2 stroke and 912 UL .   912 S yes premium auto fuel only.   NO avgas.

 

Just in from 1.5 flight on ethanol gas -- I am over 1000 hours on  ethanol gas no personally without a glitch so far.

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dave

Joined: 22 Sep 2006
Posts: 1382

Posted: Sun May 30, 2010 4:41 am Post subject: 912UL turning backwards on shutdown

Dick,

  

 Are you using avgas or auto  premium ?

  

 Sounds like pre ignition-- since you likley do not have a mixtue cut off  try shutting off the fuel vakve at shut down.

  

 912 UL will run fine on auto regular  87 grade --with or without  ethanol. 

 Acutally you might want to run a tank of ethanol regular gas through it and  see if that helps.

 Although many armchair captains will say bal bla bla about ethanol   Rtoax does infact recoment the use of it up to 10%. 

  

 Also who says that premium is always premium gas  at the pumps. I VERY  rarely use premium if ever on Rotax 2 stroke and 912 UL .   912 S yes  preium auto fuel only.   NO avgas.

  

 Just in from 1.5 flight on ethanol gas -- I am over 1000 hours onethanl gas  no personally without a gitch so far.   

  

  

 [quote]   ---

rickofudall

Joined: 19 Sep 2009
Posts: 1392
Location: Udall, KS, USA

Posted: Sun May 30, 2010 4:44 am Post subject: 912UL turning backwards on shutdown

Dick, Try dropping your idle speed so that you have to set it manually. That way you can be sure the throttle is completely closed when you shut off the mags. Check for fuel leaking into the engine through the starting carburetor, too. For the weather you're having you might want to try one range colder spark plug, also. Have you looked into the combustion chamber with a bore scope to make sure there isn't any sort of carbon build up that could cause detonation? Be sure and burp your engine after one of these run on events.  VW's (the old air cooled models) started doing this when they were leaned out for emissions control in the late 60's. It was solved by putting a solenoid and plunger over the main jet that choked off the fuel supply completely. When the solenoid failed ("Volkswagen does it again" was their advertising slogan at the time) you just let the clutch out with the tranny engaged so the engine didn't run on. Of course you don't have that option. :-}

 



Rick Girard

On Sun, May 30, 2010 at 6:54 AM,  <Catz631(at)aol.com (Catz631(at)aol.com)> wrote:

[quote]     Well, my old nemesis is back with a vengeance! Yesterday was a very hot (96degree) , muggy,lousy,typical Florida summer day. So why not go fly. I did and after shutting my engine down it slung itself backwards at least 5-10 engine revolutions (not blades) If I would have turned the mags back on, and the jugs didn't blow I betI I could have backed into my parking spot! Everyone that saw this was amazed. They have never seen an engine do this. It has done this too me before about 5 times but never turned backwards that many revolutions.

   Now I do realize that I am the ONLY person in the world that has had this problem (verified by calls to tech reps at Lockwood and LEAF) but I would like this to stop. It's beginning to give me the RA (red ass)

   I only mention this again on this forum to see if some of you gurus agree with me on the procedure I will follow from here. I plan on getting an oil sample today and sending it off for analysis for metal to see if there is any cam damage from collapsed lifters. As I understand it turning the engine backwards could ingest air into the lifters thus causing one or more to collapse thus causing scuffing of the cam lobes (ie:metal) 

   I have performed the valve lifter check after each of these events and at no time in the past have the clearances been greater than 20 thousands which according to the bulletin would indicate air in the lifters. The oil filter has always been free of metal also.

   After this last event at an outlying field, I restarted the engine, the oil pressure fluctuated a little bit at idle (as it always does since I have had the airplane) normal rpm produced steady oil pressure so I flew the aircraft back home (10 minutes) Today I might do another check for air in the lifters but I am sure if any was there, it is gone due to the 10-15 minutes of flight time home.

   I believe  the major causes of this problem are, old premium fuel (over30 days as I was on vacation) high outside temps and the fixed engine ignition timing is off somewhat. I had added octane booster to the fuel as this has helped in the past but probably not added enough.

   I have borescopped the engine cylinders and they seem relatively free of carbon (250 hrstt engine)

   Any ideas?

  I am running a Warp drive prop. I have even thought of going back to the Kiev prop. It is about a pound lighter than the Warp. It,s momentum would be less than the Warp. Maybe that would do it. Mystery!

                                    Thanks,

                                               Dick Maddux

                                               Kitfox 4

                                               Milton,Fl



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dave

Joined: 22 Sep 2006
Posts: 1382

Posted: Sun May 30, 2010 5:30 am Post subject: Re: 912UL turning backwards on shutdown

dropping idle speed sounds good but will add to gear box wear dramatically.  Most carburated auto added the solenoid in the 70s as they were higher compression engines .

Roger Lee

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

Posted: Sun May 30, 2010 5:36 am Post subject: Re: 912UL turning backwards on shutdown

Hi Dick,



Sorry to hear your having this problem. I think I would be getting a little on the RA side too. If you know the carbs are balanced and the idle is set to 1700-1800 rpm then I would dump your fuel (all of it) and try some 100LL and see if that makes a difference. It really could be old fuel and a badly reduced octane number. My first guess if the idle and carb balance is good is a fuel issue. After you try a normal shut down with 100LL, which I hope works, then try shutting off one mag for 10-15 seconds then turn the last one off, but use the 100LL first to see if it makes any difference.

_________________
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Tucson, Az.
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Float Flyr

Joined: 19 Jul 2006
Posts: 2704
Location: Campbellton, Newfoundland

Posted: Sun May 30, 2010 5:48 am Post subject: 912UL turning backwards on shutdown

Dick:  

   

Perhaps the thing to do is to shut off your fuel and starve the engine.  Similar to what they do with certified engines.  It may take a few minutes to refill the float bowl to restart though.  

   

In the meantime it sure sounds to me like your engine is running a bit too hot while taxiing and when you cut the ignition head temps cause pre-ignition... enough to spin the engine backward.  Perhaps a minute or so at a fast idle before shutting down the engine will help.  

   

Noel  

       

From: owner-rotaxengines-list-server(at)matronics.com [mailto:owner-rotaxengines-list-server(at)matronics.com] On Behalf Of Catz631(at)aol.com

 Sent: May 30, 2010 9:24 AM

 To: rotaxengines-list(at)matronics.com

 Subject: 912UL turning backwards on shutdown  

  

  

     

Well, my old nemesis is back with a vengeance! Yesterday was a very hot (96degree) , muggy,lousy,typical Florida summer day. So why not go fly. I did and after shutting my engine down it slung itself backwards at least 5-10 engine revolutions (not blades) If I would have turned the mags back on, and the jugs didn't blow I betI I could have backed into my parking spot! Everyone that saw this was amazed. They have never seen an engine do this. It has done this too me before about 5 times but never turned backwards that many revolutions.  

    

 Now I do realize that I am the ONLY person in the world that has had this problem (verified by calls to tech reps at Lockwood and LEAF) but I would like this to stop. It's beginning to give me the RA (red ass)  

    

 I only mention this again on this forum to see if some of you gurus agree with me on the procedure I will follow from here. I plan on getting an oil sample today and sending it off for analysis for metal to see if there is any cam damage from collapsed lifters. As I understand it turning the engine backwards could ingest air into the lifters thus causing one or more to collapse thus causing scuffing of the cam lobes (ie:metal)   

    

 I have performed the valve lifter check after each of these events and at no time in the past have the clearances been greater than 20 thousands which according to the bulletin would indicate air in the lifters. The oil filter has always been free of metal also.  

    

 After this last event at an outlying field, I restarted the engine, the oil pressure fluctuated a little bit at idle (as it always does since I have had the airplane) normal rpm produced steady oil pressure so I flew the aircraft back home (10 minutes) Today I might do another check for air in the lifters but I am sure if any was there, it is gone due to the 10-15 minutes of flight time home.  

    

 I believe  the major causes of this problem are, old premium fuel (over30 days as I was on vacation) high outside temps and the fixed engine ignition timing is off somewhat. I had added octane booster to the fuel as this has helped in the past but probably not added enough.  

    

 I have borescopped the engine cylinders and they seem relatively free of carbon (250 hrstt engine)  

    

  Any ideas?  

    

 I am running a Warp drive prop. I have even thought of going back to the Kiev prop. It is about a pound lighter than the Warp. It,s momentum would be less than the Warp. Maybe that would do it. Mystery!  

    

                                   Thanks,  

    

                                              Dick Maddux  

    

                                              Kitfox 4  

    

                                              Milton,Fl  

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_________________
Noel Loveys
Kitfox III-A
Aerocet 1100 Floats

sdemeyer

Joined: 31 Jul 2009
Posts: 45

Posted: Sun May 30, 2010 6:12 am Post subject: 912UL turning backwards on shutdown

I would not do this. A while back I had a P lead break and the only way to shut down was to turn the fuel off. After five minutes one carb ran out of gas before the other and it REALLY ran bad for another minute until the other carb ran out of fuel. The motor shook so bad I was worried about it remaining attached to the mount. In fact, shortly after that is when I found a large crack in my engine mount.



Scott



--- On Sun, 5/30/10, Noel Loveys <noelloveys(at)yahoo.ca> wrote:

 	  Quote: 	
		  

From: Noel Loveys <noelloveys(at)yahoo.ca>

Subject: RE: 912UL turning backwards on shutdown

To: rotaxengines-list(at)matronics.com

Date: Sunday, May 30, 2010, 6:48 AM



             

Dick:   

     

Perhaps the thing to do is to shut off your fuel and starve the engine.  Similar to what they do with certified engines.  It may take a few minutes to refill the float bowl to restart though.   

     

In the meantime it sure sounds to me like your engine is running a bit too hot while taxiing and when you cut the ignition head temps cause pre-ignition... enough to spin the engine backward.  Perhaps a minute or so at a fast idle before shutting down the engine will help.   

     

Noel   

         

From: owner-rotaxengines-list-server(at)matronics.com [mailto:owner-rotaxengines-list-server(at)matronics.com] On Behalf Of Catz631(at)aol.com

 Sent: May 30, 2010 9:24 AM

 To: rotaxengines-list(at)matronics.com

 Subject: RotaxEngines-List: 912UL turning backwards on shutdown   

  

  

       

Well, my old nemesis is back with a vengeance! Yesterday was a very hot (96degree) , muggy,lousy,typical Florida summer day. So why not go fly. I did and after shutting my engine down it slung itself backwards at least 5-10 engine revolutions (not blades) If I would have turned the mags back on, and the jugs didn't blow I betI I could have backed into my parking spot! Everyone that saw this was amazed. They have never seen an engine do this. It has done this too me before about 5 times but never turned backwards that many revolutions.   

    

 Now I do realize that I am the ONLY person in the world that has had this problem (verified by calls to tech reps at Lockwood and LEAF) but I would like this to stop. It's beginning to give me the RA (red ass)   

    

 I only mention this again on this forum to see if some of you gurus agree with me on the procedure I will follow from here. I plan on getting an oil sample today and sending it off for analysis for metal to see if there is any cam damage from collapsed lifters. As I understand it turning the engine backwards could ingest air into the lifters thus causing one or more to collapse thus causing scuffing of the cam lobes (ie:metal)    

    

 I have performed the valve lifter check after each of these events and at no time in the past have the clearances been greater than 20 thousands which according to the bulletin would indicate air in the lifters. The oil filter has always been free of metal also.   

    

 After this last event at an outlying field, I restarted the engine, the oil pressure fluctuated a little bit at idle (as it always does since I have had the airplane) normal rpm produced steady oil pressure so I flew the aircraft back home (10 minutes) Today I might do another check for air in the lifters but I am sure if any was there, it is gone due to the 10-15 minutes of flight time home.   

    

 I believe  the major causes of this problem are, old premium fuel (over30 days as I was on vacation) high outside temps and the fixed engine ignition timing is off somewhat. I had added octane booster to the fuel as this has helped in the past but probably not added enough.   

    

 I have borescopped the engine cylinders and they seem relatively free of carbon (250 hrstt engine)   

    

  Any ideas?   

    

 I am running a Warp drive prop. I have even thought of going back to the Kiev prop. It is about a pound lighter than the Warp. It,s momentum would be less than the Warp. Maybe that would do it. Mystery!   

    

                                   Thanks,   

    

                                              Dick Maddux   

    

                                              Kitfox 4   

    

                                              Milton,Fl   

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Float Flyr

Joined: 19 Jul 2006
Posts: 2704
Location: Campbellton, Newfoundland

Posted: Sun May 30, 2010 6:21 am Post subject: 912UL turning backwards on shutdown

Check again...  I think Rotax actually ALLOWS the use of up to 10% eth.

That's a stretch from recommending its use.  



Ethanol has a RON of 116 and will actually increase the RON of just about

any gas available today.  That is if you have a source of fresh 99.99% eth

to add to your gas.  Ethanol will also absorb moisture right out of the air

and because it is already in the fuel that's the wrong place for moisture to

be.



There are several other reasons why I don't like ethanol in fuel and I've

gone over those countless times.



What Dave says about, is premium actually premium, is a good question.  I

don't know anyone who has the equipment to do accurate flash testing.  I do

know that a few years ago the Newfoundland Constabulary was having problems

with a factory built hotrod they called a police car.  Technicians were sent

from GM to find out what was causing the backfiring...  after two weeks of

building and rebuilding the engine the test results from GM's own lab came

back that the fuel was a very low octane... low even for regular fuel.  The

Constab. then tested all the premium gas sold in the area and found over 50

pumps only one actually had premium fuel in it. Letters went out to all the

oil companies and the result of that was one oil company returned a letter

saying they would no longer conduct flash tests for the Constabulary.  



The answer to your problem may be as easy as changing where you buy your

gas.  If you want to foot the $50 or so bill to have a flash test done on

your fuel you may find in fact your supplier is in fact cheating you.  If

this happens be sure to inform the authorities about what is going on.

After all that is fraud.



Always buy the freshest gas you can get.  Large busy stations have more turn

over in fuel so generally have fresher fuel in their tanks.  



With ethanol, if you must use it, don't let it sit in your plane's tanks for

any longer than a day or two.  In that time ethanol can evaporate and what

doesn't evaporate will absorb some moisture (water) right out of the air.

If you have to store ethanol fuel longer than that, store it in a sealed

container not in the plane's tanks.



Noel



--

_________________
Noel Loveys
Kitfox III-A
Aerocet 1100 Floats

Float Flyr

Joined: 19 Jul 2006
Posts: 2704
Location: Campbellton, Newfoundland

Posted: Sun May 30, 2010 9:08 am Post subject: 912UL turning backwards on shutdown

I agree with Dave on this one... AVGAS should only be used as a last

alternative and if you really have to use AVGAS then get some lead scavenger

to put in it.

The idea  of having a look with a borescope has lots of merit!



Noel



--

_________________
Noel Loveys
Kitfox III-A
Aerocet 1100 Floats

Float Flyr

Joined: 19 Jul 2006
Posts: 2704
Location: Campbellton, Newfoundland

Posted: Sun May 30, 2010 9:23 am Post subject: 912UL turning backwards on shutdown

I never thought about one side running longer than the other side.  That pretty well puts paid to the idea of starving the engine.  Pulling the enricheners just before shutdown would probably flood the engine but may stop the dieseling by cooling down the combustion chamber.    

   

I suspect in warm weather you may have to go to a higher octane fuel to prevent the detonation.  

   

The idea of resetting the throttle so you will have a shutdown position sounds ok if and only if you never use that position to idle the engine.  I had my idle on my 582 set to around 600 rpm.  But I never idled the engine at that speed.  The only time I actually pulled the throttle all the way out was when landing.  As soon as I was on the water I would increase the throttle to around 1500 or even 2000 wherever the engine ran smoothest.  

   

I still think the first thing I would do is buy my gas at a different station.....  and probably try high octane gas that flashes at a higher temperature.  

   

Noel  

     

From: owner-rotaxengines-list-server(at)matronics.com [mailto:owner-rotaxengines-list-server(at)matronics.com] On Behalf Of Scott DeMeyer

 Sent: May 30, 2010 11:42 AM

 To: rotaxengines-list(at)matronics.com

 Subject: RE: 912UL turning backwards on shutdown  

  

           

I would not do this. A while back I had a P lead break and   the only way to shut down was to turn the fuel off. After five minutes one   carb ran out of gas before the other and it REALLY ran bad for another minute   until the other carb ran out of fuel. The motor shook so bad I was worried   about it remaining attached to the mount. In fact, shortly after that is when   I found a large crack in my engine mount.

   

   Scott

   

   --- On Sun, 5/30/10, Noel Loveys <noelloveys(at)yahoo.ca>   wrote:   



   From: Noel Loveys <noelloveys(at)yahoo.ca>

   Subject: RE: 912UL turning backwards on shutdown

   To: rotaxengines-list(at)matronics.com

   Date: Sunday, May 30, 2010, 6:48 AM         

Dick:   

    

Perhaps the thing to do is to shut off your fuel and   starve the engine.  Similar to what they do with certified   engines.  It may take a few minutes to refill the float bowl to restart   though.   

    

In the meantime it sure sounds to me like your   engine is running a bit too hot while taxiing and when you cut the ignition   head temps cause pre-ignition... enough to spin the engine backward.    Perhaps a minute or so at a fast idle before shutting down the engine will   help.   

    

Noel   

          

From:   owner-rotaxengines-list-server(at)matronics.com [mailto:owner-rotaxengines-list-server(at)matronics.com]   On Behalf Of Catz631(at)aol.com

   Sent: May 30, 2010 9:24 AM

   To: rotaxengines-list(at)matronics.com

   Subject: 912UL turning backwards on shutdown   

   

   

       

Well, my old   nemesis is back with a vengeance! Yesterday was a very hot (96degree) ,   muggy,lousy,typical Florida summer day. So why not go fly. I did and after   shutting my engine down it slung itself backwards at least 5-10 engine   revolutions (not blades) If I would have turned the mags back on, and the   jugs didn't blow I betI I could have backed into my parking spot!   Everyone that saw this was amazed. They have never seen an engine do this. It   has done this too me before about 5 times but never turned backwards   that many revolutions.   

      

 Now I do   realize that I am the ONLY person in the world that has had this problem   (verified by calls to tech reps at Lockwood and LEAF) but I would like this   to stop. It's beginning to give me the RA (red ass)   

      

 I only   mention this again on this forum to see if some of you gurus agree with me on   the procedure I will follow from here. I plan on getting an oil sample   today and sending it off for analysis for metal to see if there is   any cam damage from collapsed lifters. As I understand it turning the   engine backwards could ingest air into the lifters thus causing one or more   to collapse thus causing scuffing of the cam lobes (ie:metal)    

      

 I have   performed the valve lifter check after each of these events and at no time in   the past have the clearances been greater than 20 thousands which   according to the bulletin would indicate air in the lifters. The oil filter   has always been free of metal also.   

      

 After this   last event at an outlying field, I restarted the engine, the oil pressure   fluctuated a little bit at idle (as it always does since I have had the   airplane) normal rpm produced steady oil pressure so I flew the aircraft back   home (10 minutes) Today I might do another check for air in the lifters but I   am sure if any was there, it is gone due to the 10-15 minutes of flight   time home.   

      

 I   believe  the major causes of this problem are, old premium fuel   (over30 days as I was on vacation) high outside temps and the fixed engine   ignition timing is off somewhat. I had added octane booster to the fuel as   this has helped in the past but probably not added enough.   

      

 I have   borescopped the engine cylinders and they seem relatively free of carbon (250   hrstt engine)   

      

  Any ideas?   

      

 I am running   a Warp drive prop. I have even thought of going back to the Kiev prop. It is   about a pound lighter than the Warp. It,s momentum would be less than the   Warp. Maybe that would do it. Mystery!   

      

                                     Thanks,   

      

                                                Dick Maddux   

      

                                                Kitfox 4   

      

                                                Milton,Fl   

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        [quote][b]

_________________
Noel Loveys
Kitfox III-A
Aerocet 1100 Floats

rparigoris

Joined: 24 Nov 2009
Posts: 805

Posted: Sun May 30, 2010 10:11 am Post subject: Re: 912UL turning backwards on shutdown

Hi Dick

I had a 1972 Yamaha RT-2 360 single cylinder 2 stroke. Often after a highway ride in hot temps upon shut down it would give a pop and turn backwards. Easy on a bike to deal with, i would just put in gear and stall by letting out clutch. Once after a highway ride on a hot day decided to take a compression test, boy the compression gage didn't like the cylinder firing with full throttle at all! What must have happened is there was a glowing piece of carbon that fired the fuel air mixture.



Anyway with your problem:

**Give a try engaging the enriching circuit for a little bit before shut down to help cool things off, try both ways, shutting down with enrichment rich, and also after attempt to cool things a bit with enrichment lean

**I have heard that high temps of ignition boxes causes inability to shut down engine. Circuit fails with heat but when cooled down begins to work again. With such a wishy washy thing I would imagine you could get it to intermittent fire which is perhaps your problem? Anyway to add a bit of extra cooling to ignition modules?

**OK here we go, I think cooling the cylinder heads, pistons and ignition modules before shut down is in order to test. Before shut down point into wind, richen with choke and try 2750 or 3000 rpms for 15 or 20 seconds, idle with choke for 5 or 10 seconds and shut down. Try same but at idle turn off choke. 



Other stuff:

**Too lean is no good upon shutting down if a glowing piece of carbon is your culprit, did you adjust idle mixture? If not give it a go on a hot day, perhaps go just a tad bit richer.

**If glowing carbon is problem, give the plane a decarbonization. Best way of course is to pull jugs, but on my 914 I will use water. If you ever had a look at a automobile engine that has a water leak, ain't very hard to find the leak, the cylinder and head is scrubbed clean! I have owned a number of Volvo turbo station wagons, the 1983 with aircooled Garette turbo very similar to 914 turbo. After a gazillion miles they would tend to ping even with high test fuel. No problem, pick a hot summer day, go up a 1 mile not too far from my home hill with full throttle, quick pull over on side street and pour a quart of distilled water through a nipple on manifold. I add water fast enough to begin to kill motor, but increase throttle. I do this till I am about 1/4 throttle and use water injection to keep RPMs ~3,000. I will do this 3 times, first with water, second time with a can of Seafoam (get at most auto parts stores) and third time with water. I only use distilled water. Been doing that since 1983. With Rotax my idea was to try injection in manifold pressure input between cylinders on cross tube. Run a tube back to a safe distance, could probably use a super soaker for water, oil can for Seafoam.

**Another thought, Rotax is adamant you use Whacker thermal conductive compound on spark plug threads. I spoke with research guy who tested various compounds and said Whacker is hands down winner. Best use that (I am). I remember filling my brothers Jawa motorcycle carb with model aeroplane fuel, it started and began to scream (way too lean because such a high alcohol content) and when he hit kill switch, nothing, it kept on running till he put in gear and stalled.

**Is spark plugs very full of carbon to have a glowing ember and act like a glow plug?

**Are spark plugs proper heat range? This is critical. 

**True that the slower the idle is below 1800RPM the more loading of gearbox. I think I read there is 10 times more loading at idle compared to 5,000 rpm. Having carbs balanced (and mixture adjusted) helps. With a Europa if you have idle set at 1800RPM on ground, you will have a hard time landing any sort of short. Best have idle on ground (stopped) able to get to 1450 (or 1400 even), this way you can land shorter, remember when flying air flowing over prop will increase RPM. Anyway just use throttle to keep 1800 or over on ground, but in your case lowering for shut down will be a good thing.



Another thought is when you are doing 2750 or 3000 rpm choke cooling, give a mag check. See if one is either not shutting down or giving a misfire. At this RPM I doubt glowing carbon would cause this. A miss may be overheated or failing ignition module.



If you suspect ignition modules, perhaps if easy have someone spray with water mist to cool before shut down and see if that helps.



Wait a second, perhaps I remember you have a primer? If you do use that to help cool motor before shut down.



Good luck

Ron Parigoris

Roger Lee

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

Posted: Sun May 30, 2010 11:02 am Post subject: Re: 912UL turning backwards on shutdown

Hi Dick,



Are the carbs balanced?

The temporary use of 100LL is to determine if it is a poor fuel or Octane issue. Running a few gallons of 100LL will tell you that fairly quickly. If your problem goes away then you know it is nothing else. The 100LL is the easiest and cheapest up front test. Drain the fuel and put in 5 gal. of 100LL and go fly again. If it still happens then don't chase the fuel issue again and look at other things. You need to rule out one issue at a time to make sure you find the problem. This may also be a gearbox issue in part. Does your 912 have an overload clutch and how many hours?  I need to do a little more checking, but do the other test first.

_________________
Roger Lee
Tucson, Az.
Rotax Instructor & Rotax IRC
Light Sport Repairman
Home 520-574-1080 TRY HOME FIRST
Cell 520-349-7056

malannx(at)bigpond.com
Guest

Posted: Mon May 31, 2010 3:54 am Post subject: 912UL turning backwards on shutdown

Dick, I had that problem. Engine would sometimes stop okay, sometimes  diesel, sometimes run backwards. Turned out to be a crook wire in the p lead  making a partial circuit. Very hit and mis. Now have my idle set for 1200 rpm.  Never idle this slow except when shutting down. I turn off the mags seperately.  Gives the smoothest shutdown, not the usual drum full of bolts sound.

 Malcolm Feguson

   [quote][b]

Dick Maddux

Joined: 24 Jun 2008
Posts: 516
Location: Milton, Fl

Posted: Mon May 31, 2010 4:47 am Post subject: 912UL turning backwards on shutdown

Dave,Richard,Scott,Noel,Ron,Roger....Holy Mackerel are you guys alive or what? I certainly can't answer each one of you but you guys have certainly come through with some great ideas!! (I apologize if I left anyone out.)

  To answer some questions, I have been using auto fuel premium (no ethanol) I went to premium because the run on occurred almost every time with regular when the outside temp was hot. ( even though as you say Dave the 912UL is supposed to use regular)

  I will lower the idle speed even further for shutdown purposes and turn off the mags one at a time (with a pause) as you suggest Roger. That makes sense and I have not been doing that. My idle speed is about 1700 rpm now.

  I don't have a choke, only a primer. I might give it a squirt at shutdown as you suggest Ron. Cooling fuel might stop this from happening. I will also check the idle mixture as you say it might be on the lean side. Scott, you brought up a good point on turning the fuel off. It makes sense that one float bowl could go dry before the other causing an imbalance. I would be willing to bet that that is why Rotax uses the ignition to stop the engine vs a mixture or some sort of a fuel shutoff. No possibility of an imbalance that way

   You know the "water cleansing" of cylinders was brought up by a friend of mine Ron. He too used to do that to get rid of carbon in the cylinders of his bikes and cars and had great success. I have borescoped my cylinders and I do have a small amount of carbon but not much. I will kept that in the back of my mind. I suppose you could spray water into the inlets of each carb simultaneously. However I do remember that we had water injection on the old DC6 (C-118) I used to fly while in the Navy. It was disabled so we never used it but as I recall it raised the compression and produced more power. It was only to be used when you absolutely, positively had to get off the ground. I believe a few jugs were blown so they disabled it.

  As far as plugs go I have been using the standard recommended for the 912UL. I don't remember the number off hand. Any suggestions for a colder plug?

  

 So here is the plan for shutdown:

   (1) Fresh premium auto fuel (avgas if this doesn't work)

   (2) reduce idle speed for shutdown purposes (1400 or so)

   (3) turn off mags one at a time (shot of prime if necessary to cool cylinders)

  

 I generally don't have a problem in the winter. It is this horrible summer heat that seems to bring it on. The engine temps at cruise (and idle) are fine though. I am running about 185 CHT,195-200 Oil temp ,1300-1350 EGT on 95 degree days.

  Sorry to be writing a novel here but early morning, good coffee, wife still sleeping, makes for good times. Thanks again for all your help !!!

                                                        

                                                         Dick Maddux

                                                         912UL

                                                         Milton,Fl

  [quote][b]

rickofudall

Joined: 19 Sep 2009
Posts: 1392
Location: Udall, KS, USA

Posted: Mon May 31, 2010 5:30 am Post subject: 912UL turning backwards on shutdown

Dick, When I was a kid with my first VW I used to visit with an old German mechanic who had his own independent Porsche garage. He showed me a way to decarbon. I've used it, it works. It will take two people to do it with a 912, one to spray, the other on the throttle. Mix 1 part kerosene in 3 parts water in a spray bottle, you'll need two. Shake vigorously as you would oil and vinegar dressing. Raise RPM of warm engine so it does not stall. Spray into carbs. Watch color of exhaust, it will be blackish as the carbon comes out, then light gray as you're just processing the water / kerosene mix. You're done when engine idles normally after a good runup. 



Rick Girard



On Mon, May 31, 2010 at 7:47 AM,  <Catz631(at)aol.com (Catz631(at)aol.com)> wrote:

[quote]     Dave,Richard,Scott,Noel,Ron,Roger....Holy Mackerel are you guys alive or what? I certainly can't answer each one of you but you guys have certainly come through with some great ideas!! (I apologize if I left anyone out.)

   To answer some questions, I have been using auto fuel premium (no ethanol) I went to premium because the run on occurred almost every time with regular when the outside temp was hot. ( even though as you say Dave the 912UL is supposed to use regular)

   I will lower the idle speed even further for shutdown purposes and turn off the mags one at a time (with a pause) as you suggest Roger. That makes sense and I have not been doing that. My idle speed is about 1700 rpm now.

   I don't have a choke, only a primer. I might give it a squirt at shutdown as you suggest Ron. Cooling fuel might stop this from happening. I will also check the idle mixture as you say it might be on the lean side. Scott, you brought up a good point on turning the fuel off. It makes sense that one float bowl could go dry before the other causing an imbalance. I would be willing to bet that that is why Rotax uses the ignition to stop the engine vs a mixture or some sort of a fuel shutoff. No possibility of an imbalance that way

    You know the "water cleansing" of cylinders was brought up by a friend of mine Ron. He too used to do that to get rid of carbon in the cylinders of his bikes and cars and had great success. I have borescoped my cylinders and I do have a small amount of carbon but not much. I will kept that in the back of my mind. I suppose you could spray water into the inlets of each carb simultaneously. However I do remember that we had water injection on the old DC6 (C-118) I used to fly while in the Navy. It was disabled so we never used it but as I recall it raised the compression and produced more power. It was only to be used when you absolutely, positively had to get off the ground. I believe a few jugs were blown so they disabled it.

   As far as plugs go I have been using the standard recommended for the 912UL. I don't remember the number off hand. Any suggestions for a colder plug?

  

 So here is the plan for shutdown:

   (1) Fresh premium auto fuel (avgas if this doesn't work)

   (2) reduce idle speed for shutdown purposes (1400 or so)

   (3) turn off mags one at a time (shot of prime if necessary to cool cylinders)

  

 I generally don't have a problem in the winter. It is this horrible summer heat that seems to bring it on. The engine temps at cruise (and idle) are fine though. I am running about 185 CHT,195-200 Oil temp ,1300-1350 EGT on 95 degree days.

   Sorry to be writing a novel here but early morning, good coffee, wife still sleeping, makes for good times. Thanks again for all your help !!!

                                                        

                                                         Dick Maddux

                                                         912UL

                                                         Milton,Fl

   	  Quote: 	
		  



ist" target="_blank">http://www.matronics.com/Navigator?RotaxEngines-List

tp://forums.matronics.com

_blank">http://www.matronics.com/contribution



	


[b]

_________________
The smallest miracle right in front of you is enough to make you happy....

Roger Lee

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

Posted: Mon May 31, 2010 1:42 pm Post subject: Re: 912UL turning backwards on shutdown

Hi Dick,



Unless you idle excessively then I would expect you to see black carbon coloring, but not a substantial or thick build up. The black coating would be normal especially if you have any time on the engine. If I remember your engine hours you don't have that many. I just don't see this as a carbon issue.

_________________
Roger Lee
Tucson, Az.
Rotax Instructor & Rotax IRC
Light Sport Repairman
Home 520-574-1080 TRY HOME FIRST
Cell 520-349-7056

Dick Maddux

Joined: 24 Jun 2008
Posts: 516
Location: Milton, Fl

Posted: Tue Jun 01, 2010 5:24 am Post subject: 912UL turning backwards on shutdown

Thanks again for you replys with more good ideas ! Malcolm, it is good to hear that I was not the only guy who had this problem !  Rick I appreciate the decarbonising tip. That is a great method and I will keep it for future referance.At thispoint, as Roger mentioned, I believe my hours on the engine are a bit low for that and borescoping shows little carbon but later on I will probaly use that method (other engines also...my Triumph TR3 as an example) Vic ,thanks for your input on the propeller. When I mounted the Kiev prop previously,even though it was the wrong one (for 100 hp with 2.43 ratio), the engine sure ran smooth and shutdown appeared to be easier. I will order the proper "lightweight" prop.

  Yesterday,I completed the "valve check" and the clearances were ok so hopefully no air in the lifters. I lowered the idle to aprox 1200-1400. (will only use that momentarily for engine shutdown) 

  I did a test hop which was cut short by a huge thunderstorm approaching our field. The shutdown was done at aprox 12- 1400 rpm one mag at a time and was a none event.

                                                            Dick Maddux

                                                            912UL

                                                            Milton,Fl

Roger Lee

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

Posted: Wed Jun 02, 2010 9:23 pm Post subject: Re: 912UL turning backwards on shutdown

How big a Warp prop and is it nickled edge? This could be a damaged overload clutch.

_________________
Roger Lee
Tucson, Az.
Rotax Instructor & Rotax IRC
Light Sport Repairman
Home 520-574-1080 TRY HOME FIRST
Cell 520-349-7056

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