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Rotax 912 Idle

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kuffel(at)cyberport.net
Guest

Posted: Mon Nov 29, 2010 12:46 pm Post subject: Rotax 912 Idle

John Hauck said:



<< 912ULS indicates 2,500 to 3,000 rpm with the throttle closed gliding.  It 

is more like 2,000 rpm.  It idles

1,600 rpm on the ground static.  >>



My Zenith CH701 friend has a 912S.  It has the characteristic on the ground 

of stopping when the throttle is pulled to full idle. As his friendly Flight 

Advisor I find this worrisome if not downright unsafe. I've tried to get him 

to increase his idle stop screws but he views it as a deliberate design 

"feature" to replace the absent mixture idle cutoff.    Any comments or 

experience to assuage my fears or convince him of the error of his ways?



Tom Kuffel

Whitefish, MT

John Hauck

Joined: 09 Jan 2006
Posts: 4639
Location: Titus, Alabama (hauck's holler)

Posted: Mon Nov 29, 2010 1:40 pm Post subject: Rotax 912 Idle

My Zenith CH701 friend has a 912S.  It has the characteristic on the ground

of stopping when the throttle is pulled to full idle. As his friendly Flight

Advisor I find this worrisome if not downright unsafe. I've tried to get him

to increase his idle stop screws but he views it as a deliberate design

"feature" to replace the absent mixture idle cutoff.    Any comments or

experience to assuage my fears or convince him of the error of his ways?



Tom Kuffel

Whitefish, MT





Tom K/Gang:



The 912 operators manual indicates the idle speed to be 1,400 rpm minimum.



No mention of "deliberate design feature to replace the absent mixture idle 

cutoff."



I believe if Rotax wanted a mixture idle cutoff, they would have equipped 

the 912 with a mixture control.



Never lost a 912 with the throttle closed during an approach, and don't want 

to.  For that matter, never had a 912 quit running in flight, except when I 

screwed up and tried to fly with contaminated fuel.  I didn't know the fuel 

was contaminated because I did not drain fuel after I obtained it from an 

unreliable source, even though I thought, at the time, both places were 

reliable aviation fuel suppliers.



I have found with my one 912UL and two 912ULS's, they all like to idle 

around 1,500 to 1,600 rpm.



john h

mkIII

Titus, Alabama

_________________
John Hauck
MKIII/912ULS
hauck's holler
Titus, Alabama

zeprep251(at)aol.com
Guest

Posted: Sun Dec 05, 2010 10:26 am Post subject: Rotax 912 Idle

Tom,

 It,s like teaching a pig to whistle,it wastes your time and annoys the pig.

 

 G.Aman  

 

  --

kuffel(at)cyberport.net
Guest

Posted: Sun Dec 05, 2010 10:35 pm Post subject: Rotax 912 Idle

<<  My Zenith CH701 friend has a  912S.  It has the characteristic on the ground of stopping when the  throttle is pulled to full idle >>  

 << It,s like teaching a pig to whistle,it  wastes your time and annoys the pig.

G.Aman >>

 

Actually he has been pretty responsive to most  of my suggestions and did a thorough and careful AC90-89 style preparation to  his successful first flight.

  

 After showing him John's response to my query he  has agreed before his second flight to increase his idle set screws  1/2 turn at a time until he gets a stable idle above 1400.  However since  he is an (anti)snowbird, the next flight might not be until spring given the  recent weather here.

  

 Tom Kuffel

 Whitefish, MT



   [quote][b]

zeprep251(at)aol.com
Guest

Posted: Mon Dec 06, 2010 5:56 am Post subject: Rotax 912 Idle

Tom,

 Didn't sound that promising in your first post.Johns advice carries a lot more weight than most.My friend has a Savannah /912S.We set it mechanically, closing the throttle plates completely, then use a feeler gauge for base adjustment ,then 2 vac gauges on the crossover tube ports to get a very smooth idle at 1600.We also have a dynamic balancer we purchased as a group that made his 912 incredibly

 

  

   smooth at RPM.

 G.Aman

 

   

 

  --

John Hauck

Joined: 09 Jan 2006
Posts: 4639
Location: Titus, Alabama (hauck's holler)

Posted: Mon Dec 06, 2010 6:11 am Post subject: Rotax 912 Idle

We also have a dynamic  balancer we purchased as a group that made his 912  incredibly



 

 smooth at  RPM.

G.Aman

  

  

  

 



 



  Gary A/Gang:

  

 What kind of "dynamic balancer"  do you have?

  

 I am assuming this is a prop balancer.

  

 I bought a pair of good quality, viscous dampened vacuum gauges, a couple  years ago, to balance my carbs on the 912.  However, there was some  discrepancy in readings between the two.  After a couple tries at using the  gauges to balance, I chucked them, and use mechanical balance only.  Seemed  I was doing a better job mechanically than with the vacuum gauges.

  

 The mud daubers have built nest in my prop hub while I was recovering  from my injuries.  I got most of them out before I flew the other day, but  need to remove the prop and extension in order to do a proper job of  cleaning.  Then I have to decide how to block the empty prop hub holes to  prevent them from homesteading  on my engine again.

  

 28F, clear and cold in Titus, Alabama.

  

 john h

 mkIII

   [quote][b]

_________________
John Hauck
MKIII/912ULS
hauck's holler
Titus, Alabama

williamtsullivan(at)att.n
Guest

Posted: Mon Dec 06, 2010 6:36 am Post subject: Rotax 912 Idle

John- For plugging/blocking stray holes, try spray foam in a can.  Marketed under "Really Great Stuff", or a similar name.  Available at Home Depot, Lowe's, or a hardware store.  Expands to fit, can be trimmed with a saw or knife, weighs nothing, and won't hurt anything if it falls out.  Cheap, too.

  

                                          Bill Sullivan



--- On Mon, 12/6/10, John Hauck <jhauck(at)elmore.rr.com> wrote:



  	  Quote: 	
		  

From: John Hauck <jhauck(at)elmore.rr.com>

Subject: Re: Rotax 912 Idle

To: kolb-list(at)matronics.com

Date: Monday, December 6, 2010, 9:08 AM



     

  We also have a dynamic balancer we purchased as a group that made his 912 incredibly



 

 smooth at RPM.

G.Aman

  

  

  

 



 



  Gary A/Gang:

  

 What kind of "dynamic balancer"  do you have?

  

 I am assuming this is a prop balancer.

  

 I bought a pair of good quality, viscous dampened vacuum gauges, a couple years ago, to balance my carbs on the 912.  However, there was some discrepancy in readings between the two.  After a couple tries at using the gauges to balance, I chucked them, and use mechanical balance only.  Seemed I was doing a better job mechanically than with the vacuum gauges.

  

 The mud daubers have built nest in my prop hub while I was recovering from my injuries.  I got most of them out before I flew the other day, but need to remove the prop and extension in order to do a proper job of cleaning.  Then I have to decide how to block the empty prop hub holes to prevent them from homesteading  on my engine again.

  

 28F, clear and cold in Titus, Alabama.

  

 john h

 mkIII

 	  Quote: 	
		  



ollow target=_blank>www.aeroelectric.com

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 [quote][b]

zeprep251(at)aol.com
Guest

Posted: Mon Dec 06, 2010 6:39 am Post subject: Rotax 912 Idle

John,

 web site for balancer is RPXTECH.com

 

   G.Aman

 

  

   

 

   

 

  --

John Hauck

Joined: 09 Jan 2006
Posts: 4639
Location: Titus, Alabama (hauck's holler)

Posted: Mon Dec 06, 2010 6:45 am Post subject: Rotax 912 Idle

John- For plugging/blocking stray holes,  try spray foam in a can.  Marketed under "Really Great Stuff", or a similar  name.  Available at Home Depot, Lowe's, or a hardware store.  Expands  to fit, can be trimmed with a saw or knife, weighs nothing, and won't hurt  anything if it falls out.  Cheap, too.  

                                           Bill Sullivan



  

  

  

 Bill S/Gang:

  

 Think that would work in bolt holes in the prop  hub?

  

 I used silicone seal to fill holes in the gear box.   Hesitated to use it on steel after some severe corrosion using it on a 4130 tail  wheel strut.

  

 john h

 mkIII

 Titus, Alabama

  

  

  

   [quote][b]

_________________
John Hauck
MKIII/912ULS
hauck's holler
Titus, Alabama

herbgh(at)nctc.com
Guest

Posted: Mon Dec 06, 2010 6:54 am Post subject: Rotax 912 Idle

Might try the non acetic acid silicone sealant...I am guessing that that was why you have corrosion?   Never bought any so not sure of brands etc...The Long ez guys use it to make fiberglass lay ups which they mold around their engines for cooling baffles...Herb 



 At 08:43 AM 12/6/2010, you wrote:

 [quote] John- For plugging/blocking stray holes, try spray foam in a can.  Marketed under "Really Great Stuff", or a similar name.  Available at Home Depot, Lowe's, or a hardware store.  Expands to fit, can be trimmed with a saw or knife, weighs nothing, and won't hurt anything if it falls out.  Cheap, too. 

  

                                          Bill Sullivan



  

  

  

 Bill S/Gang:

  

 Think that would work in bolt holes in the prop hub?

  

 I used silicone seal to fill holes in the gear box.  Hesitated to use it on steel after some severe corrosion using it on a 4130 tail wheel strut.

  

 john h

 mkIII

 Titus, Alabama

  

  

  



 [b]

by0ung(at)brigham.net
Guest

Posted: Mon Dec 06, 2010 8:04 am Post subject: Rotax 912 Idle

Actually he has been pretty responsive to most  of my suggestions and did a thorough and careful AC90-89 style preparation to  his successful first flight.

  

 After showing him John's response to my query he  has agreed before his second flight to increase his idle set screws  1/2 turn at a time until he gets a stable idle above 1400.  However since  he is an (anti)snowbird, the next flight might not be until spring given the  recent weather here.

  

 Tom Kuffel

 Whitefish, MT

  

  

 tom

  

 while pulling a mixture control to kill most  aircraft engines  is a design feature,,,  it is done by a separate  control,  and can't be done by accident while adjusting the throttle in an  emergency or normal routine.   if he wanted a way to kill the engine  if the mag switches failed...   have him fix up a control that will  shut the fuel off either at the tanks or just before the carbs.   it  would take a bit longer to kill the engine because of the fuel in the float  bowl..  but it would be better than killing the engine on short final only  to find that because of wind, you needed a bit more power to make the  runway.

  

 maybe because he has agreed to 1400 rpm at idle...  this may be too late to be of help...   if he created a stop on the  throttle quadrant  that would keep the engine at a good idle speed...   and have a way to disable the stop by depressing another control at the  same time.  then he could, only after overcoming the throttle stop,   be able to pull the throttle to stop the engine.  

  

 the idle stop screws would be the best way to  control the idle speed...  as cable stretch would alter the settings if  using a throttle stop.

  

 boyd young

 mkIII  912



   [quote][b]

by0ung(at)brigham.net
Guest

Posted: Mon Dec 06, 2010 8:13 am Post subject: Rotax 912 Idle

John,

web site for balancer is  RPXTECH.com



 G.Aman



 

 

 	  Quote: 	
		  >>>>>>>>>>>

  
	


 Garry....   does the balancer change any  between flights,,,  and therefore take a little time to rebalance upon  start up...   or is it quite stable between flights.

  

 boyd



   [quote][b]

zeprep251(at)aol.com
Guest

Posted: Mon Dec 06, 2010 9:54 am Post subject: Rotax 912 Idle

John,

 The balancer tells you how much weight to add  and where to add it.I put only a few grams under the prop attach bolts (washers in my case)or nuts.I have the info in the certificate holder in the airplane so I can't recall exactly how much weight total we added,but it was a few grams.We left the reflector tape on on as well,,just a small spot..The chart in the plane is a segmented circle showing degrees

 

   and the weight added at those locations.

 

  

   G.Aman

 

   

 

  --

zeprep251(at)aol.com
Guest

Posted: Mon Dec 06, 2010 3:06 pm Post subject: Rotax 912 Idle

Boyd,

 Sorry,After reading my first post it sounded like an accessory that bolted on .It's a procedure using this equipment.I thought my Jabiru was fairly smooth,but I could feel the difference after we balanced the prop.

 G.Aman MK3C Jabiru 2200A 600hrs

 

   

 

  

   

 

   

 

  --

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