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reverse prop rotation at shut down

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Dick Maddux

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

Posted: Sun Jan 20, 2013 6:25 am Post subject: reverse prop rotation at shut down

I didn't know quite what to call this. As many of you know I have had a on  going problem with the prop rotating backwards at shut down sometimes. It's not  really diseling (I don' think) ..Maybe it stops at the top of the pawl in  the gearbox and flips backwards. I don't know. I have had the carbs redone  ,gearbox rebuilt,prop replaced,borescoped cylinders,etc.

  The only thing that appears to stop this from happening is to pull  the throttle back to about 1200 rpm (or much less) at shutdown.

  Anyway, my question revolves around the possibility of ingesting air  into the lifters. My prop has gone around as much as 3 revolutions in  reverse direction. So in each case I have done the lifter check making sure I  have no more than .020 clearance between the push rods and the rocker arm  (per the service inst)

  I have done this so many times that I am seriously  considering attaching my cowl with Velcro !

  At no time have the clearances on the valves exceeded the parameter.  

  I highly suspect that rotating you prop backwards,providing there are  no open oil lines,etc is not the big deal that Rotax makes it out to be.  Obviously I am not going to do it on purpose but 3 full revolutions  backward and no air ingestion ? On at least 10 occasions ?

  Stupid engine !..but it really does run well other than this quirk,it  starts at one blade,smooth... it's just perplexing.

                                                                         Dick Maddux

                                                                         912 UL

 [quote][b]

rlborger(at)mac.com
Guest

Posted: Sun Jan 20, 2013 8:04 am Post subject: reverse prop rotation at shut down

Hi Dick,



I notice that you say: "The only thing that appears to stop this from happening is to pull the throttle back to about 1200 rpm (or much less) at shutdown." That's exactly how I shut my engine down.  I let it idle at 1800-2000 RPM for a bit to cool the turbo and just kind of quiet things down.  Then for shutdown I pull the throttle all the way back, let the engine drop to about 1200 RPM and as it hits that 1200 I kill both ignition switches to stop.  That's the only time I let the RPM go below 1800.  

Some folks may ask why I even have the throttle set to allow RPM below 1800.  Good question.  I had it set that way originally and found out that the darn airplane (as a monowheel) didn't want to come down or land with that much power being made.  I could slow-flight a thousand feet down the runway in ground effect at 1800 RPM before it'd settle in.  So I set the throttle to allow me retard it below that 1800 idle on final approach.  Then, with the throttle fully back, the aircraft descended nicely showing 1800 RPM (rather than 2100 at the previous setting) and at the flare I bump the throttle to keep the RPM at a satisfactory level and I could land without coasting the full length of the runway.  Things appear to have changed a bit now that it's a tri-gear.  I have to fly it a bit more to see just how it has changed.

 Blue skies & tailwinds,

Bob Borger

Europa XS Tri, Rotax 914, Airmaster C/S Prop.

Little Toot Sport Biplane, Lycoming Thunderbolt AEIO-320 EXP

3705 Lynchburg Dr.

Corinth, TX  76208-5331

Cel: 817-992-1117

rlborger(at)mac.com (rlborger(at)mac.com)



 

 

On Jan 20, 2013, at 8:24 AM, Catz631(at)aol.com (Catz631(at)aol.com) wrote:

     I didn't know quite what to call this. As many of you know I have had a on  going problem with the prop rotating backwards at shut down sometimes. It's not  really diseling (I don' think) ..Maybe it stops at the top of the pawl in  the gearbox and flips backwards. I don't know. I have had the carbs redone  ,gearbox rebuilt,prop replaced,borescoped cylinders,etc.

  The only thing that appears to stop this from happening is to pull  the throttle back to about 1200 rpm (or much less) at shutdown.

  Anyway, my question revolves around the possibility of ingesting air  into the lifters. My prop has gone around as much as 3 revolutions in  reverse direction. So in each case I have done the lifter check making sure I  have no more than .020 clearance between the push rods and the rocker arm  (per the service inst)

  I have done this so many times that I am seriously  considering attaching my cowl with Velcro !

  At no time have the clearances on the valves exceeded the parameter.  

  I highly suspect that rotating you prop backwards,providing there are  no open oil lines,etc is not the big deal that Rotax makes it out to be.  Obviously I am not going to do it on purpose but 3 full revolutions  backward and no air ingestion ? On at least 10 occasions ?

  Stupid engine !..but it really does run well other than this quirk,it  starts at one blade,smooth... it's just perplexing.

                                                                         Dick Maddux

                                                                         912 UL

BARRY CHECK 6

Joined: 15 Mar 2011
Posts: 738

Posted: Sun Jan 20, 2013 8:10 am Post subject: reverse prop rotation at shut down

Guys:



I am on the Rotax list because I am very interested in getting a Ch-601 and many of them have Rotax engines.  I would jump at the chance of getting one with a O-200 or O-235.  I just can not justify in the slightest a Rotax engine, because of issues like Dick is reporting.  I may be forced into a Rotax, only to swap it out.

 But, Dick, I think I have a suggestion that may help in your situation.  Set the engine at high idle - KILL the MAG/Spark first - Then the fuel.  If the problem still occurs then look at the possibility of a Hot Spot (Pre-Ignition) 

 Jerking an engine in the reverse direction is not a good thing no matter how you look at it.  Not even good for the airframe.  

Barry



On Sun, Jan 20, 2013 at 9:24 AM,  <Catz631(at)aol.com (Catz631(at)aol.com)> wrote:

 [quote]     I didn't know quite what to call this. As many of you know I have had a on  going problem with the prop rotating backwards at shut down sometimes. It's not  really diseling (I don' think) ..Maybe it stops at the top of the pawl in  the gearbox and flips backwards. I don't know. I have had the carbs redone  ,gearbox rebuilt,prop replaced,borescoped cylinders,etc.

  The only thing that appears to stop this from happening is to pull  the throttle back to about 1200 rpm (or much less) at shutdown.

  Anyway, my question revolves around the possibility of ingesting air  into the lifters. My prop has gone around as much as 3 revolutions in  reverse direction. So in each case I have done the lifter check making sure I  have no more than .020 clearance between the push rods and the rocker arm  (per the service inst)

  I have done this so many times that I am seriously  considering attaching my cowl with Velcro !

  At no time have the clearances on the valves exceeded the parameter.  

  I highly suspect that rotating you prop backwards,providing there are  no open oil lines,etc is not the big deal that Rotax makes it out to be.  Obviously I am not going to do it on purpose but 3 full revolutions  backward and no air ingestion ? On at least 10 occasions ?

  Stupid engine !..but it really does run well other than this quirk,it  starts at one blade,smooth... it's just perplexing.

                                                                         Dick Maddux

                                                                         912 UL

  	  Quote: 	
		  



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

tp://forums.matronics.com

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



	


[b]

brian.davies(at)clara.co.
Guest

Posted: Sun Jan 20, 2013 9:28 am Post subject: reverse prop rotation at shut down

Barry,

 

If you treat a Rotax like a Lyc/Cont  it will protest.  Switching off the ignition at high idle will cause the problem being described.  I was taught to close the throttle completely and then switch off one mag, and then both mags.  That way the engine stops without kick back.  The gearbox arrangement prevents the engine stopping softly like a Lycoming.  It will always stop suddenly as if it has seized.  Once you get used to it, it will not give you any problems.

 

Regards

 

Brian

 

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

Sent: 20 January 2013 16:10

To: rotaxengines-list(at)matronics.com

Subject: Re: reverse prop rotation at shut down

 

Guys:

 



I am on the Rotax list because I am very interested in getting a Ch-601 and many of them have Rotax engines.  I would jump at the chance of getting one with a O-200 or O-235.  I just can not justify in the slightest a Rotax engine, because of issues like Dick is reporting.  I may be forced into a Rotax, only to swap it out.



But, Dick, I think I have a suggestion that may help in your situation.  Set the engine at high idle - KILL the MAG/Spark first - Then the fuel.  If the problem still occurs then look at the possibility of a Hot Spot (Pre-Ignition) 



Jerking an engine in the reverse direction is not a good thing no matter how you look at it.  Not even good for the airframe.  



 



Barry

On Sun, Jan 20, 2013 at 9:24 AM, <Catz631(at)aol.com (Catz631(at)aol.com)> wrote:

I didn't know quite what to call this. As many of you know I have had a on going problem with the prop rotating backwards at shut down sometimes. It's not really diseling (I don' think) ..Maybe it stops at the top of the pawl in the gearbox and flips backwards. I don't know. I have had the carbs redone ,gearbox rebuilt,prop replaced,borescoped cylinders,etc.



 The only thing that appears to stop this from happening is to pull the throttle back to about 1200 rpm (or much less) at shutdown.



 Anyway, my question revolves around the possibility of ingesting air into the lifters. My prop has gone around as much as 3 revolutions in reverse direction. So in each case I have done the lifter check making sure I have no more than .020 clearance between the push rods and the rocker arm (per the service inst)



 I have done this so many times that I am seriously considering attaching my cowl with Velcro !



 At no time have the clearances on the valves exceeded the parameter. 



 I highly suspect that rotating you prop backwards,providing there are no open oil lines,etc is not the big deal that Rotax makes it out to be. Obviously I am not going to do it on purpose but 3 full revolutions backward and no air ingestion ? On at least 10 occasions ?



 Stupid engine !..but it really does run well other than this quirk,it starts at one blade,smooth... it's just perplexing.



                                                                       Dick Maddux



                                                                       912 UL

 	  Quote: 	
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  [quote][b]

Alan Carter

Joined: 02 Jul 2012
Posts: 378
Location: Kent, England.

Posted: Sun Jan 20, 2013 5:50 pm Post subject: Re: reverse prop rotation at shut down

Hi all.

It does seem to have a lot of problems Staring and Stopping, seems more have problems than don,t.

The design, the prop coming to a sudden stop, which is normal for the Rotax engine, so it may be, but my common scene tells me it not an ideal way an engine should stop, 

I run my engine for 3 minutes at idle to cool the turbo down, and stop it at the lowest RPMs i can achieve. 

Your problem sound like Pre ignition the engine it hot.

My starting Kick back is Detonation of the fuel, or the timing to far in advance and the piston not getting over TDC.

During crank at starter speed i can not see to much hot air being made.

Only me making it,saying Stupid engine.

My Prop is a PV 50

Just found the receipt for the battery, 22/09/2009

ODYSSEY EXTREME RACING BATTERY 25 (16 APP/HRS-680 AMPS CRANK)  priced Â£100 now is that a good battery ?? it seems to turn it over OK ?



What you need is the old model aeroplane starter clipped to the spinner then the  little engine had no choice which way it was going to go, Remember those days, or perhaps its just us old boys that made models on the end of a wire. 



I would guess my plane has the standard fitted starter motor. 

When i get round to it i will fit a soft start but for me it means fitting a starter button.

Alan

max8992

Joined: 28 Jul 2011
Posts: 142

Posted: Mon Jan 21, 2013 1:00 am Post subject: reverse prop rotation at shut down

Hi there all !

 

Brian says : “If you treat a Rotax like a Lyc/Cont  it will protest... I was taught to close the throttle completely and then switch off one mag, and then both mags ...Once you get used to it, it will not give you any problems”.

Coming from old Lyc / Conti world I happen to discover the same trick to shut down with my first 912ULS on the Europa and apply it now to the second on my MCR4S (also a bit surprised by its attitude at starting I’m still considering to implement a “soft start kit”). It seems not to have an impact on the cycle-life, both running smoothly after more than 450 hours.

Max  Cointe

mcointe(at)free.fr (mcointe(at)free.fr)

F-PMLH Europa XS_TriGear

Kit #560-2003 912ULS/AirmasterAP332 450 hours

 

F-PLDJ Dyn’Aéro MCR 4S 



Kit #27-2002 912ULSFR/MTProp MTV7A 1550 heures



 

  [quote][b]

_________________
Max8992
Europa XS #560 F-PMLH

Alan Carter

Joined: 02 Jul 2012
Posts: 378
Location: Kent, England.

Posted: Mon Jan 21, 2013 2:28 am Post subject: Re: reverse prop rotation at shut down

Hi.

450 hours, !

My Honda Civic did 330,000 miles god knows how many hours that would be over 18 years and was still as good as the first day i had it  .

Its an engine, should run all its life without any major  problems.

Why do you all seem the think an areo engine should be any different

Alan.

rlborger(at)mac.com
Guest

Posted: Mon Jan 21, 2013 4:47 am Post subject: reverse prop rotation at shut down

Alan,



Aero engines are operated in a different manner to auto engines.  Auto engines normally don't run at more than 25% of their rated power.  The engine in my Ford F-150 is capable of 450 ft-lbs of torque and 390 HP at 5000 RPM but rarely runs over 2500 RPM.  It's just lazing along at highway speeds.  And they very rarely, if ever, are called on to provide 100% power.



Aero engines normally run in the 65%-100% range of their power.  And Aero engines are routinely operated at 100% power for extended periods of time during takeoff and initial climb out.  Engines with fixed pitch props always climb at 100% power.  Engines with C/S props may drop back to 90% for extended climb.  Then in cruise they run at 65%-75% or greater power continuously.  As a result there's considerably more operating stress on an aero engine than an auto engine.



And that doesn't take into account the differences in operating environment at sea level to 6000 feet vs sea level to 12,000 feet and sometimes much higher.



Blue skies & tailwinds,

Bob Borger

Europa XS Tri, Rotax 914, Airmaster C/S Prop.

Little Toot Sport Biplane, Lycoming Thunderbolt AEIO-320 EXP

3705 Lynchburg Dr.

Corinth, TX  76208-5331

Cel: 817-992-1117

rlborger(at)mac.com



On Jan 21, 2013, at 4:28 AM, Alan Carter <alancarteresq(at)onetel.net> wrote:






Hi.

450 hours, !

My Honda Civic did 330,000 miles god knows how many hours that would be over 18 years and was still as good as the first day i had it  .

Its an engine, should run all its life without any major  problems.

Why do you all seem the think an areo engine should be any different

Alan.

Dick Maddux

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

Posted: Mon Jan 21, 2013 5:55 am Post subject: reverse prop rotation at shut down

Thanks for all your replies. 

 I have tried shutting down at high idle...that didn't work as then it  really wants to go backward  !

 Going from a Warp to a Kiev prop,which is lighter ,helped a lot but still  once in a while I  get the reverse rotation if I am not judicious in  low rpm shutdown. 

  The engine only has 350 hrs total and the timing is fixed of course.  It starts and runs great. It really only has that one consistent bug at shutdown  I have to watch for. Again if I shut down at around 1000-1200 rpm,it seems  to do OK. I too taxi (at) 1800 rpm. Shutdown is one mag off,then the next off,then  both off (per Rotax suggestion)

  I will live with this occasional anomaly but am getting mighty tired  of doing the valve check each time it does this and of course the one time  I don't,it will suck air into the lifters !

  

  Bob,

   My short final rpm in my Kitfox is around 2100  which equates  to 1800 rpm on the deck. I too had to learn to adjust to this as I would float  awhile in ground effect. (throttle is fully closed) but I am used to it now. I  can always slip or use more flaps for more drag.

                                                                            Dick Maddux

                                                                           912  UL 

  

 [quote][b]

Alan Carter

Joined: 02 Jul 2012
Posts: 378
Location: Kent, England.

Posted: Mon Jan 21, 2013 6:28 am Post subject: Re: reverse prop rotation at shut down

Hi Bob.

Happy new year to you. 

Yes all correct,but some engines total millions of hours,I still thing the Rotax is not trouble free and could be better, 

I,m no aero engine expert, but for this sort of engine which seems to start OK on snow mobiles maybe should have have something like a slip and grip clutch if there is such a thing,?

Disconnect the propeller, Start and Stop the engine without that huge propeller going round, once started slip the clutch in to engage the prop, and stop in the same way so the prop just free wheels down.

Now if some-one had designed something like this we would not have all these problems. Maybe also there is a reason this can,t be done and i,m talking out of my ass, but maybe not.?

Alan

max8992

Joined: 28 Jul 2011
Posts: 142

Posted: Mon Jan 21, 2013 6:50 am Post subject: reverse prop rotation at shut down

Alan,



I won't comment which part of your body talks here as internet doesn't

transmit odor (yet) 

Basically the reducer includes a clutch but with no manual directive. Adding

one would add heavy components and additional causes of failure (like

existing on turboprops).



Max  Cointe

mcointe(at)free.fr

F-PMLH Europa XS_TriGear

Kit #560-2003 912ULS/AirmasterAP332 450 hours



F-PLDJ Dyn’Aéro MCR 4S 

Kit #27-2002 912ULSFR/MTProp MTV7A 1550 heures

-----Message d'origine-----

De : owner-rotaxengines-list-server(at)matronics.com

[mailto:owner-rotaxengines-list-server(at)matronics.com] De la part de Alan

Carter

Envoyé : lundi 21 janvier 2013 15:28

À : rotaxengines-list(at)matronics.com

Objet : Re: reverse prop rotation at shut down




--> <alancarteresq(at)onetel.net>



Hi Bob.

Happy new year to you. 

Yes all correct,but some engines total millions of hours,I still thing the

Rotax is not trouble free and could be better, I,m no aero engine expert,

but for this sort of engine which seems to start OK on snow mobiles maybe

should have have something like a slip and grip clutch if there is such a

thing,?

Disconnect the propeller, Start and Stop the engine without that huge

propeller going round, once started slip the clutch in to engage the prop,

and stop in the same way so the prop just free wheels down.

Now if some-one had designed something like this we would not have all these

problems. Maybe also there is a reason this can,t be done and i,m talking

out of my ass, but maybe not.?

Alan





Read this topic online here:



http://forums.matronics.com/viewtopic.php?p=392808#392808

_________________
Max8992
Europa XS #560 F-PMLH

Alan Carter

Joined: 02 Jul 2012
Posts: 378
Location: Kent, England.

Posted: Mon Jan 21, 2013 7:47 am Post subject: Re: reverse prop rotation at shut down

Hello Max.

Thousands of hours on Turbo props never had any trouble, proper jet engines log up 10s of millions of hours, in fact i have many hours on all types of light aircraft and can honestly say the Rotax seems to be among one the the most temperamental i have come across in starting and stopping. Once its going it seem to work fine. From the post on the form you must admit it is troublesome in starting, Hence the introduction of the Soft start dammage sprags ,ete ete.



 

Alan

BARRY CHECK 6

Joined: 15 Mar 2011
Posts: 738

Posted: Mon Jan 21, 2013 8:33 am Post subject: reverse prop rotation at shut down

Allen:



You are 100% correct.  Well, at least it should run trouble free to TBO.  And TBO is a certified number by the Government.  Cars don't get that type of certification.  Well, maybe - There is the Lemon Law.. Maybe engines should also have a Lemon Law.   AFTER ALL - A plane is NOT  like a car.  You can't pull over at a cloud and do maintenance or request a tow truck..  

 One thing I have learned about Cars, Planes and People - The Cars and Planes can fail - But the People will not admit the Car, Plane, or Engine they spent good money on STINKS.  They did nothing in the design or building of the engine but will swear it is the best thing since sliced bread.  I have no problem about bitching about a car, plane or engine that has more bugs than a freshly burred corps in a pine box.  Lycoming had huge problems until the lawyers fixed them all.  My Lycoming had huge problems until it was Majored for a third time (it seams to be working - ONLY time will tell).

 The two issues are: 

1 - They are mechanical - They are not perfect.

2 - They are built by people - And surely you know they are not perfect.

By the way Allen, a fellow I know has 588,000+ Miles on a GMC Jimmy - GM purchased the car and dismantled the engine - They said it had about as much ware as a 12,000 mile engine.  It is in some type of record book.  Oh, he also ONLY used Mobile 1 Full Synthetic Oil and changed the oil ever 2,500 miles.  Now That is CRAZY!

 



All I want is an engine to do TBO and not have to fly every second worrying about a Emergency Place to Land.

And no - I do not do that.  

Barry



 On Mon, Jan 21, 2013 at 5:28 AM, Alan Carter <alancarteresq(at)onetel.net (alancarteresq(at)onetel.net)> wrote:

[quote] --> RotaxEngines-List message posted by: "Alan Carter" <alancarteresq(at)onetel.net (alancarteresq(at)onetel.net)>

 

 

Hi.

 450 hours, !

 My Honda Civic did 330,000 miles god knows how many hours that would be over 18 years and was still as good as the first day i had it  .

 Its an engine, should run all its life without any major  problems.

 Why do you all seem the think an areo engine should be any different

 Alan.

 

 

 

 

 Read this topic online here:

 

 

http://forums.matronics.com/viewtopic.php?p=392791#392791

 

 

 

 

 

 

 

 ===========

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

 ===========

 http://forums.matronics.com

 ===========

 le, List Admin.

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

 ===========

 

 

 

 



[b]

Alan Carter

Joined: 02 Jul 2012
Posts: 378
Location: Kent, England.

Posted: Mon Jan 21, 2013 9:19 am Post subject: Re: reverse prop rotation at shut down

Hi Barry.

Well Barry 588,000 is a long way, but i still think 330000 miles i have some sort of record,as the car was left outside all year round never, never serviced at a garage, and all i ever did was change the oil and filters every 10,000.plus the usual odds and ends like brakes.

I do get some flak  on my posts ,no expert on anything,but voice my ideas for discussion, as i found out in Aerobatics there is always some-one who can do it better, so open for the input from others on the Forum,be it good or bad,

However i left myself a bit open. don,t think i will mention my anatomy again 

 .

Alan

BARRY CHECK 6

Joined: 15 Mar 2011
Posts: 738

Posted: Mon Jan 21, 2013 10:51 am Post subject: reverse prop rotation at shut down

Alan:



I do not feel you left yourself open at all.  It is a positive way of thinking what SHOULD be expected from an engine, especially an aircraft engine where you put your life and those of your passengers to the test every time you fly.  

 



Yes, 330,000 miles is quite great - And you take care of your car engine the way I do.  My Hyundai has 225,095 miles as of this morning.   And I change the oil twice a year whether it needs it or not 

 Oh, No burping required on the Hyundai either.  No $8.00/Qt oil either.  No $20.00 oil filter either. No $25.00/Pt of Cam Guard either.  GRANTED!  Our cars are used way more often than our planes and we MUST do what we can to safeguard our play-toy investment.  AND you have to remember this: Our planes are used at 65% to 75% of power for 95% of the flight; 100% during takeoff.  Our cars are about 20% of the HP during cruse - BIG DIFFERENCE.  Some day I am going to install my spare fuel flow gauge in the car and play with the Fuel flow BHP numbers just to see what they really are.

 



Barry

On Mon, Jan 21, 2013 at 12:19 PM, Alan Carter <alancarteresq(at)onetel.net (alancarteresq(at)onetel.net)> wrote:

 [quote]--> RotaxEngines-List message posted by: "Alan Carter" <alancarteresq(at)onetel.net (alancarteresq(at)onetel.net)>

  

 Hi Barry.

 Well Barry 588,000 is a long way, but i still think 330000 miles i have some sort of record,as the car was left outside all year round never, never serviced at a garage, and all i ever did was change the oil and filters every 10,000.plus the usual odds and ends like brakes.

  I do get some flak  on my posts ,no expert on anything,but voice my ideas for discussion, as i found out in Aerobatics there is always some-one who can do it better, so open for the input from others on the Forum,be it good or bad,

  However i left myself a bit open. don,t think i will mention my anatomy again

  .

 Alan

 

    [Wink]

 

 

[b]

Alan Carter

Joined: 02 Jul 2012
Posts: 378
Location: Kent, England.

Posted: Mon Jan 21, 2013 11:10 am Post subject: Re: reverse prop rotation at shut down

Hi All.

Just to clarify on this ,Iwas told i should not compare a Rotax with a Turbo Prop, absolutely right, and i was not.

All i am saying for Â£25000 i expect an engine with better starting and stopping.

And these problem's are serious as they could cost you a new engine.

Alan

Dick Maddux

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

Posted: Tue Jan 22, 2013 6:05 am Post subject: reverse prop rotation at shut down

Roger,

  I had the gearbox disassembled and re shimmed about 65 hrs ago.  It didn't make any difference at all, it still goes backward  sometimes. 

  For what it is worth, the engine is a mid 90's 912 UL with about 350  hrsTT.

  The only thing that appears to help is to pull the throttle back  until the engine sounds like a "grinder' (not good on the box I am sure) around  1000 rpm and then shut it down .

  The much lighter Kiev (vs Warp) really reduced these events though.  The last one was my fault as I shut down about 1400 rpm.

  Why hasn't it sucked air into the lifters so far ? It turns backwards  at least 3 full revolutions. They told us in all my Rotax classes to never turn  the prop backwards or this could happen. I have had the reverse business at  least 10 times and on each occasion I have done the valve check and  it never caught any air in the valves. Oil filter analysis doesn't reveal  any metal either.

  I do like to work on engines,airframes ,etc which is a good thing  cause the Rotax has given me a lot of practice and I learn more about it. This  engine is a mystery in many ways requiring research and advice from gurus such  as yourself (which I thank you for !) I am sure that if I had a younger engine I  would not have the problems that I do.(broken coil wires,old HD wires,spark  plug caps,etc)

  I am still adverse to taking  my plane on a long trip  though as there would be little to no support if the engine decides to act  up again. We do have a guy here in Pensacola that flys his CT back and  forth to the West coast and thinks nothing of it. An AI friend of mine(with  my assist) help to maintain it for him and it has been very  reliable. 

  By the way,I was able to get new NGK plug caps for $6.30 each vs the  almost $50 Rotax wanted. They are the same part number. Overall I saved about  $500 on my plug harness replacement and it did solve my misfire problem. The  engine runs even smoother now !

                                                                                             Dick Maddux

                                                                                              Rotax 912UL

                                                                                              Kitfox  4                                                                 

 [quote][b]

ricardourio(at)gmail.com
Guest

Posted: Tue Jan 22, 2013 7:47 am Post subject: reverse prop rotation at shut down

It´s like autoignition. Maybe a hot point inside engine can do it, like excessive carbonization, of a incomplete very rich burn, or maybe wrong spark plugs. Have you tested your magneto switch to see if it is grounding appropriately the magneto wire ? 



Ricardo Urio



2013/1/22  <Catz631(at)aol.com (Catz631(at)aol.com)>

[quote]      Roger,

  I had the gearbox disassembled and re shimmed about 65 hrs ago.  It didn't make any difference at all, it still goes backward  sometimes. 

  For what it is worth, the engine is a mid 90's 912 UL with about 350  hrsTT.

  The only thing that appears to help is to pull the throttle back  until the engine sounds like a "grinder' (not good on the box I am sure) around  1000 rpm and then shut it down .

  The much lighter Kiev (vs Warp) really reduced these events though.  The last one was my fault as I shut down about 1400 rpm.

  Why hasn't it sucked air into the lifters so far ? It turns backwards  at least 3 full revolutions. They told us in all my Rotax classes to never turn  the prop backwards or this could happen. I have had the reverse business at  least 10 times and on each occasion I have done the valve check and  it never caught any air in the valves. Oil filter analysis doesn't reveal  any metal either.

  I do like to work on engines,airframes ,etc which is a good thing  cause the Rotax has given me a lot of practice and I learn more about it. This  engine is a mystery in many ways requiring research and advice from gurus such  as yourself (which I thank you for !) I am sure that if I had a younger engine I  would not have the problems that I do.(broken coil wires,old HD wires,spark  plug caps,etc)

  I am still adverse to taking  my plane on a long trip  though as there would be little to no support if the engine decides to act  up again. We do have a guy here in Pensacola that flys his CT back and  forth to the West coast and thinks nothing of it. An AI friend of mine(with  my assist) help to maintain it for him and it has been very  reliable. 

  By the way,I was able to get new NGK plug caps for $6.30 each vs the  almost $50 Rotax wanted. They are the same part number. Overall I saved about  $500 on my plug harness replacement and it did solve my misfire problem. The  engine runs even smoother now !

                                                                                             Dick Maddux

                                                                                              Rotax 912UL

                                                                                              Kitfox  4                                                                 

  	  Quote: 	
		  



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

tp://forums.matronics.com

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



	


[b]

Dick Maddux

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

Posted: Wed Jan 23, 2013 6:09 am Post subject: reverse prop rotation at shut down

Ricardo,

  Thanks for your reply.

  I have checked the "P" leads with an ohmmeter and they check good. A  bore scope revealed nothing abnormal in the cylinders. 

  I let the engine idle for a minute or two prior to shutdown in order  to cool any "hot spots"

  Most of the time I don't have this reverse problem. It is a once in  awhile thing usually related to higher engine rpm at shutdown when I am not  focusing on it.

  This is kind of similar to the on going problem of a friend's  Paradise P-1. His engine has a vibration at cruise rpm that we can't "nail down"  We have gone thru the carbs,engine mounts,airframe,rebuilt gearbox twice,changed  the prop,plugs,.....etc. The "ghost in the machine" I guess. 

  I can live with my problem as it is controllable but that constant  vibration at cruise would drive me nuts !

                                                               

                                                                      Dick Maddux

                                                                      912 UL

 [quote][b]

Thom Riddle

Joined: 10 Jan 2006
Posts: 1597
Location: Buffalo, NY, USA (9G0)

Posted: Thu Jan 24, 2013 5:25 am Post subject: Re: reverse prop rotation at shut down

Dick,



I know a guy who has been flying a Kolb Slingshot w/ 912UL for a long time. For several years he complained about what he called a "Rum Rum Rum" sound that he could never cure. Sort of like the harmonics sound you get with a twin engine recip airplane when the two engines are not quite in synch. Or tuning a guitar with a tuning fork and the guitar is not quite in tune. He did everything everyone suggested to no avail. Finally, he sent his gearbox to Lockwood (I think) and it took a changing of the gear set to rid it of that sound. My memory of the details could be off.



He may be on this Rotax List, if not, I know he is on the Kolb Matronics list. It might be worth contacting him if the "vibration at cruise" you friend is having is similar to what he had. His name is Ted Cowan.

_________________
Thom Riddle
Buffalo, NY (9G0)

Don't worry about old age... it doesn't last very long.
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