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Why would my Yak 52 m14p lose power?
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dsavarese0812(at)bellsout
Guest

Posted: Fri Dec 19, 2008 4:38 am Post subject: Why would my Yak 52 m14p lose power?

Sounds like it could very well be carb ice.   I would remove and inspect ALL fuel screens/filters including the one at the  rear of the carburetor just above the fuel inlet.  It's a 22 mm  nut.

 Dennis

  

 [quote]   ---

george(at)gesoco.com
Guest

Posted: Fri Dec 19, 2008 4:53 am Post subject: Why would my Yak 52 m14p lose power?

Dennis,

     As you know the M14P engine has a pressure carb. the  fuel is injected down stream of the venturii. It is very similar to a throttle  body injection system. As fuel is not evaporating in the low pressure area  (lower temperature area per Boyles law) by the venturi, the pressure carburetor  is almost immune to carb ice. (particularly in Texas)

     It is much more likely that the engine loaded up at  reduced throttle. Reading between the lines, the pilot admits he does not have  much experience with radial engines. 

 I always try to teach new guys to use a throttle reduction to zero  thrust rather than to completely pull the throttle back. If you really need the  dynamic braking of a idling engine, then at least :CLEAR" the engine by  periodically opening the throttle and clearing out the loaded up spark plugs.  

  

 George Coy

  



   From:  owner-m14pengines-list-server(at)matronics.com  [mailto:owner-m14pengines-list-server(at)matronics.com] On Behalf Of A.  Dennis Savarese

Sent: Friday, December 19, 2008 7:37 AM

To:  m14pengines-list(at)matronics.com

Subject: Re: Why  would my Yak 52 m14p lose power?

 

 Sounds like it could very well be carb ice.   I would remove and inspect ALL fuel screens/filters including the one at the  rear of the carburetor just above the fuel inlet.  It's a 22 mm  nut.

 Dennis

  

 [quote]   ---

dsavarese0812(at)bellsout
Guest

Posted: Fri Dec 19, 2008 5:17 am Post subject: Why would my Yak 52 m14p lose power?

I completely agree with you George.  However  a mutual friend, Dave Harcourt, is 100% convinced he has experienced carb ice on  a least a couple of occasions and had to use the carb heat to cure the problem  and will not back down from that theory under any circumstances.

  

 Excellent words of wisdom on use of the  throttle too.

  

 Merry Christmas to you, Cliff and your  families.

 Dennis

 [quote]   ---

doug(at)ripleyair.com
Guest

Posted: Fri Dec 19, 2008 5:50 am Post subject: Why would my Yak 52 m14p lose power?

Be careful about being 100% convinced about  anything....a good friend was convinced he was experiencing carb ice on his  Lycoming O-360....carb heat helped, but he later (more than a year later!)  realized it was a fuel flow problem........

  

 Remember.....

 1.  Ain't no future in beating your head  against the wall

 2.  Keep doing the same thing and you'll get  the same results

 3.  If you can't fix it with a hammer, you  have an electrical problem

  

  

 [quote]   ---

BPA(at)bpaengines.com
Guest

Posted: Fri Dec 19, 2008 7:37 am Post subject: Why would my Yak 52 m14p lose power?

COOL dude. I like the paint scheme. Have a good time fishing?   

   

--

flushjohnson(at)charter.n
Guest

Posted: Fri Dec 19, 2008 9:17 am Post subject: Why would my Yak 52 m14p lose power?

I had a similar problem with mt CJ with a M14  conversion. Discovered the primer was not installed properly , thought it was  off when it was still in the on position there fore was loading up in low ower  setting. Could not get idel adjustment correct because ideling to rich. Made  correction to primer (made sure in off position) solved problem.

 [quote]   ---

Claytonfly(at)comcast.net
Guest

Posted: Fri Dec 19, 2008 11:44 am Post subject: Why would my Yak 52 m14p lose power?

Dennis

  I would get hold of Jim Kimball Enterprises http://www.jimkimballenterprises.com/web/index.php they  have a mod that you can do to the carb. that will probably take care of your  problem.

  

 John  Clayton

 Pitts  Model 12 builder

  

 09/03/00 MIXTURE CONTROL, ACCELERATOR PUMP MODS,  STUMBLE



The mixture is not actually  slaved to the throttle.  It is controlled by a barrometric pressure  anneroid.  This system senses the barr. press. and sets the mixture  accordingly.  From 0 to 5000ft. it stays full rich.  From 5000ft up it  leans out.  There is an accelerator pump curcuit that is coupled to the  throttle to ad extra fuel when the throttle is rapidly advanced.  This  accell pump is the cause of the "stumble" that most M-14Ps have when the  throttle is pushed up after being at idle or near idle for a while.  This  can be adjusted out with a series of different needles etc to get it right for  your condititions and piloting.  However, nobody does this and they live  with the stumble.  There is a carb mod done here that we have done on our  Model 12 and a few other M-14Ps around here.  It involves plugging this  accell pump passage.  Very simple, and very effective.  The throttle  response on our 12 is fantastic, like a dragster.  KK 

 [quote]   --

MONTY(at)bpaengines.com
Guest

Posted: Fri Dec 19, 2008 12:07 pm Post subject: Why would my Yak 52 m14p lose power?

George Coy is partially correct with his comments regarding throttle operation.  Also, the M14 is a dynamic counterweighted engine and as such it is good operating practice to never let the propeller “ drive “ the engine, particularly at high forward airspeed as the counterweight bushings can become “ detuned “ , which means they get  

Literally get hammered out of shape.  I don’t know how susceptible the M14 is to this phenomenon but a reduction geared Lycoming is extremely sensitive to it.  

   

I think it is a bad assumption to think that the Russian throttle body carburetor will not make carb. Ice.  Here are the reasons I think it can.  There is a pressure drop  

Across the carburetor venturi which, under high humidity conditions can change water vapor to water in droplet form and some temperature reduction takes place because of the expansion after the airflow leaves the venturi.   Shortly after this event, fuel is metered into the lower pressure area and is evaporated.  Evaporation is endothermic, which means the temperature is lowered.  Now we have liquid water at a reduced temperature and if the reduced temperature is 32 dF, presto, carburetor ice.  

   

I have heard this same argument regarding the famous Bendix Pressure Carbs. and I can testify that a PS-5 WILL make carburetor ice under the above conditions.  

   

My 2 pence  

Monty Barrett  

   

   

--

eddiemoranii(at)yahoo.com
Guest

Posted: Sat Dec 20, 2008 7:03 am Post subject: Why would my Yak 52 m14p lose power?

[quote]Mark,  



I am not an expert by any means but I agree on the ice theory.  I also have a picture of the accel plug fix.  I would plug that if you have not already.  The following info came from Dennis a few years ago.



See attached.  Item #10 is a  plug (11 mm I believe) and under the plug is the acceleration pump jet.   The jet has a slot in it just like a slotted screw.  Use a straight blade  screwdriver to remove.  Plug it and reinstall.



The figure is attached.



Eddie Moran

N320VT 

Murphy Moose



--- On Thu, 12/18/08, markgreenway <geewhizmark(at)gmail.com> wrote:

[quote]From: markgreenway <geewhizmark(at)gmail.com>

Subject: Why would my Yak 52 m14p lose power?

To: m14pengines-list(at)matronics.com

Date: Thursday, December 18, 2008, 9:30 PM



 	  Quote: 	
		  --> M14PEngines-List message posted by: "markgreenway"

<geewhizmark(at)gmail.com>



Hello Guys



    Any idea why I lost power and had to make a forced landing ,because when

crossing midfield for landing, the motor lost power when I

 throttled back. It

never totally died and it regained power once on the ground

Carb_drawing.doc

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Download

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Carb_drawing.doc

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Downloaded:

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dstroud(at)storm.ca
Guest

Posted: Sat Dec 20, 2008 7:32 am Post subject: Why would my Yak 52 m14p lose power?

I'm slightly confused now. We're removing a plug to  uncover the jet below it. Your last sentence says    'plug it and  reinstall' , do you mean to 

 remove the jet, plug it ( the jet ) somehow, then  reinstall the plugged jet and cover it with the first plug? Is this process done  on the Huosai 

 engine too ? thanks..

  

 David Stroud     Ottawa,  Canada

Christavia C-FDWS

Fairchild 51 replica

under  construction  C-FYXV

 [quote]   ---

eddiemoranii(at)yahoo.com
Guest

Posted: Sat Dec 20, 2008 8:19 am Post subject: Why would my Yak 52 m14p lose power?

David, << We're removing a plug to  uncover the jet below it.>>  Yes, #10 on the diagram is the plug (11mm) that you pull to get to the jet.



The jet unscrews, comes out, has a little hole in it.  You plug that somehow..(weld, JB, etc.).  Then reinsert the jet and reinstall the 11mm plug.  



My engine ran much better after the mod with no noted lag in acceleration.



Eddie



--- On Sat, 12/20/08, DAVID STROUD <dstroud(at)storm.ca> wrote:

[quote]From: DAVID STROUD <dstroud(at)storm.ca>

Subject: Re: Re: Why would my Yak 52 m14p lose power?

To: m14pengines-list(at)matronics.com

Date: Saturday, December 20, 2008, 10:32 AM



       I'm slightly confused now. We're removing a plug to  uncover the jet below it. Your last sentence says    'plug it and  reinstall' , do you mean to 

 remove the jet, plug it ( the jet ) somehow, then  reinstall the plugged jet and cover it with the first plug? Is this process done  on the Huosai 

 engine too ? thanks..

  

 David Stroud     Ottawa,  Canada

Christavia C-FDWS

Fairchild 51 replica

under  construction  C-FYXV

 [quote]   ---

yakplt(at)yahoo.com
Guest

Posted: Sun Dec 21, 2008 11:43 am Post subject: Why would my Yak 52 m14p lose power?

I'll take some flames if necessary, but I feel I must point out that this mod was actually intended for fixing the throttle lag experienced in a lot of M-14PF model engines (400HP) and NOT for the M-14P model, which is the straight 360 HP engine.  A normal M-14P engine should run perfectly WITHOUT needing this modification.  

  

 Point number two.  Something that has worked normally in the past, and then suddenly starts working abnormally, or in a way different from in the past is usually happening because something has changed and not because something needs to be modified.  I think this problem meets that description.  

  

 This particular engine lost power when throttled back.  It did not stumble and falter when the throttle was advanced from idle on the deck.  This does not sound like an accelerator pump issue.... ice possibly, water in the fuel, low fuel pressure, a tank venting problem, you name it... lots of possible causes, but I would be very hesitant to recommend the accel pump mod on ANY engine for the described problem.  

  

 Respectfully, 

  

 Mark Bitterlich 

 N50YK.  

  

 p.s.  Run this by Sergei Boriak, or better yet Vladimir Yastremski... I think you will find they will agree.  

  

 

 

 

   From: Eddie Moran <eddiemoranii(at)yahoo.com>

To: m14pengines-list(at)matronics.com

Sent: Saturday, December 20, 2008 11:18:38 AM

Subject: Re: Re: Why would my Yak 52 m14p lose power?



    David, << We're removing a plug to uncover the jet below it.>>  Yes, #10 on the diagram is the plug (11mm) that you pull to get to the jet.



The jet unscrews, comes out, has a little hole in it.  You plug that somehow..(weld, JB, etc.).  Then reinsert the jet and reinstall the 11mm plug.  



My engine ran much better after the mod with no noted lag in acceleration.



Eddie



--- On Sat, 12/20/08, DAVID STROUD <dstroud(at)storm.ca> wrote:

 [quote]From: DAVID STROUD <dstroud(at)storm.ca>

Subject: Re: Re: Why would my Yak 52 m14p lose power?

To: m14pengines-list(at)matronics.com

Date: Saturday, December 20, 2008, 10:32 AM



    I'm slightly confused now. We're removing a plug to uncover the jet below it. Your last sentence says    'plug it and reinstall' , do you mean to 

 remove the jet, plug it ( the jet ) somehow, then reinstall the plugged jet and cover it with the first plug? Is this process done on the Huosai 

 engine too ? thanks..

  

 David Stroud     Ottawa, Canada

Christavia C-FDWS

Fairchild 51 replica

under  construction C-FYXV

 [quote] ---

culpspecial(at)yahoo.com
Guest

Posted: Sun Dec 21, 2008 11:54 am Post subject: Why would my Yak 52 m14p lose power?

I had a similar experience.

  

 Looking at my log book I have about 2000 hours behind  M-14Ps.   About 1200 doing acro flying airshows over the last 15 years.  Never had much problem with them.  My wife did have a failure a few years ago and here is a link.

  

 http://www.avweb.com/news/safety/182990-1.html

 http://www.avweb.com/news/newacft/182747-1.html

  

 I was talking  with George about this yesterday and he has quite a bit of experience with these motors also.

  

 A while back I was making passes and noticed a drop in RPM during each pass.  

 I would do a 180 and things would clear up without any throttle change and come around for another high speed pass.

  

 I also noticed a vibration and harmonics change.

  

 It was pretty cool and humid out that morning and that might have been a contributing factor.

  

 But, looking back on this when I finished mowing the hangar I realize it was just the taller grass causing the John Deere to bog down and probably not carb ice.

  

 I know the Kohler is dynamically balanced and may be similar to the M-14P in that reguard.  Because of this I always tell my students never to make drastic power reductions as this may let the mower stall as you will be caught in the deep grass.

  

 So what's this got to do the the M-14?  I don't know.  Kinda like the PS 5 carbs and geared Lycs.  Not much!

  

 Listen to George and people that have actually had experience with this.<grin>

  

 Ben Morfue and Les Crowder figured out the jet problem in about 1990 and most guys have been using it since.

  

 It has worked on about 200 odd M-14Ps I have had experience with the last 18 years.

  

 One other thing.  I can't say how many M-14Ps I have seen with the mixture cap still sealed from the factory.  It helps to adjust this after the motor has a few hours on it along with the jet mod.  It is that cover that has safety wire and a lead stamp on it on the right side of the motor.  Can be adjusted with motor running.

  

 Sincerely,

  

 Steve Culp

 Culp's Specialties

 www.culpsspecialties.com

  

 



--- On Fri, 12/19/08, Monty Barrett Sr <MONTY(at)bpaengines.com> wrote:



 [quote]From: Monty Barrett Sr <MONTY(at)bpaengines.com>

Subject: RE: Why would my Yak 52 m14p lose power?

To: m14pengines-list(at)matronics.com

Date: Friday, December 19, 2008, 2:10 PM



       

George Coy is partially correct with his comments regarding throttle operation.  Also, the M14 is a dynamic counterweighted engine and as such it is good operating practice to never let the propeller “ drive “ the engine, particularly at high forward airspeed as the counterweight bushings can become “ detuned “ , which means they get

 

Literally get hammered out of shape.  I don’t know how susceptible the M14 is to this phenomenon but a reduction geared Lycoming is extremely sensitive to it.

 

 

 

I think it is a bad assumption to think that the Russian throttle body carburetor will not make carb. Ice.  Here are the reasons I think it can.  There is a pressure drop

 

Across the carburetor venturi which, under high humidity conditions can change water vapor to water in droplet form and some temperature reduction takes place because of the expansion after the airflow leaves the venturi.   Shortly after this event, fuel is metered into the lower pressure area and is evaporated.  Evaporation is endothermic, which means the temperature is lowered.  Now we have liquid water at a reduced temperature and if the reduced temperature is 32 dF, presto, carburetor ice.

 

 

 

I have heard this same argument regarding the famous Bendix Pressure Carbs. and I can testify that a PS-5 WILL make carburetor ice under the above conditions.

 

 

 

My 2 pence

 

Monty Barrett

 

 

 

 

 

--

dsavarese0812(at)bellsout
Guest

Posted: Sun Dec 21, 2008 7:01 pm Post subject: Why would my Yak 52 m14p lose power?

Mark,

 There are many, many M14P's, 360 HP engines that  exhibit the throttle response hesitation.  The problem is not limited to  the PF engine only.  The problem of throttle response hesitation can be  reduced by changing the accelerator pump jet down to a smaller  diameter.  The smallest accelerator pump jet is .9 mm and I can say  from experience, changing to the .9 mm jet does not totally eliminate the  problem on those engines that exhibit the problem.

  

 I too have plugged many an accelerator pump jet  to stop the hesitation problem on both P and PF engines.  My opinion is,  the accelerator pump jet provides additional fuel during WOT which  helps to cool the cylinders (richer mixture).  I'm not sure what the  long term impact might be by plugging the accelerator pump jet.

  

 Dennis

  

 [quote]   ---

yakplt(at)yahoo.com
Guest

Posted: Sun Dec 21, 2008 8:01 pm Post subject: Why would my Yak 52 m14p lose power?

Was not trying to disagree or start an argument with you Dennis .  Just did not believe that this cure was applicable to the problem being described.  Respectfully, I still do not.  

  

 Regarding the stumble in throttle movement.  I have talked to many people about this pressure carb.  A lot of people think they have this thing fully figured out and I have some doubts there since their explanations seem to differ from the mechanics I have talked to that are Russians themselves and were trained in that country.  I know that my personal understanding is much less than complete to put it mildly.  I do not have the personal first hand experience to back this up, but from what I have seen one Russian do, it appears that the "P" model engines that I have seen stumble are usually able to be cured without plugging the accel pump.  Some cases have required changing air bleed jets to values that "by the book" seemed to be rather extreme, but the change then allowed the accel pump jet to be pretty much  left alone, or operated withinn normal ranges but never plugged.  This is problematic in that this puts  strong suspicion on proper operation of the diaphragms in that the engine was possibly over rich in the transition  range to begin with.  My comment about P vs. PF engines was not meant to imply that the problem could not happen with a P model, but that in every case I have seen it could be cured by exercising the complete range of adjustments possible with this carb, further that while it may have been tried and used successfully with the P model, that according to my sources, it was originally intended for the PF model where this problem happens more often.  I am not sure who "invented" this mod.... Seems to me I was told once... might have been you, George Coy,  I really am not sure.  I hope someone chimes in regarding this so that if I am wrong on that point,   I can be corrected.   Given that there is no magic in how an engine burns fuel, and that there are a lot of P models that run perfectly  without the accel jet plugged, it seems to me that an engine that does not run right has something out of adjustment (or just not working right internally) and does not need a carb design change.  No question that the mod works on some engines, but to me it is a matter of robbing Peter to pay Paul.  

  

 Bottom line, no one around here has a flow bench for these things that I know of, or has tried to truly tackle over-hauling one and then charting the flow curves on this side of the pond, and since the darn things are no longer in production, long term users may eventually switch to fuel injection anyway.   

  

 While New Bern is not a big airport for Russian engines, we have had 5 aircraft with P model engines, all of which ran perfectly without stumble, and another 4 with PF models, ALL of which stumble some worse than others.  

 

 I was told that the carb does have a circuit for WOT mixture enrichment.  I was also informed the operator can pull the throttle back until a very small change in manifold pressure is seen in order to save fuel with minimum performance loss.  Both pieces of info came from Russian sources directly, if that means anything.  

  

 Mark Bitterlich

  

   

 From: A. Dennis Savarese <dsavarese0812(at)bellsouth.net>

To: m14pengines-list(at)matronics.com

Sent: Sunday, December 21, 2008 7:00:34 PM

Subject: Re: Re: Why would my Yak 52 m14p lose power?

 DIV { MARGIN:0px;}   Mark,

 There are many, many M14P's, 360 HP engines that exhibit the throttle response hesitation.  The problem is not limited to the PF engine only.  The problem of throttle response hesitation can be reduced by changing the accelerator pump jet down to a smaller diameter.  The smallest accelerator pump jet is .9 mm and I can say from experience, changing to the .9 mm jet does not totally eliminate the problem on those engines that exhibit the problem.

  

 I too have plugged many an accelerator pump jet to stop the hesitation problem on both P and PF engines.  My opinion is, the accelerator pump jet provides additional fuel during WOT which helps to cool the cylinders (richer mixture).  I'm not sure what the long term impact might be by plugging the accelerator pump jet.

  

 Dennis

  

 [quote] ---

jan.mevis(at)informavia.b
Guest

Posted: Sun Dec 21, 2008 10:59 pm Post subject: Why would my Yak 52 m14p lose power?

And also all the Russian mechanics that I know of in Europe, would agree ….  

   

Jan Mevis  

RA2005K  

       

From: owner-m14pengines-list-server(at)matronics.com [mailto:owner-m14pengines-list-server(at)matronics.com] On Behalf Of Yak Pilot

 Sent: zondag 21 december 2008 20:43

 To: m14pengines-list(at)matronics.com

 Subject: Re: Re: Why would my Yak 52 m14p lose power?  

  

  

       

I'll take some flames if necessary, but I feel I must point out that this mod was actually intended for fixing the throttle lag experienced in a lot of M-14PF model engines (400HP) and NOT for the M-14P model, which is the straight 360 HP engine.  A normal M-14P engine should run perfectly WITHOUT needing this modification.    

    

   

    

Point number two.  Something that has worked normally in the past, and then suddenly starts working abnormally, or in a way different from in the past is usually happening because something has changed and not because something needs to be modified.  I think this problem meets that description.    

    

   

    

This particular engine lost power when throttled back.  It did not stumble and falter when the throttle was advanced from idle on the deck.  This does not sound like an accelerator pump issue.... ice possibly, water in the fuel, low fuel pressure, a tank venting problem, you name it... lots of possible causes, but I would be very hesitant to recommend the accel pump mod on ANY engine for the described problem.    

    

   

    

Respectfully,   

    

   

    

Mark Bitterlich   

    

N50YK.    

    

   

    

p.s.  Run this by Sergei Boriak, or better yet Vladimir Yastremski... I think you will find they will agree.    

    

   

    



    

    

         

  

From: Eddie Moran <eddiemoranii(at)yahoo.com>

 To: m14pengines-list(at)matronics.com

 Sent: Saturday, December 20, 2008 11:18:38 AM

 Subject: Re: Re: Why would my Yak 52 m14p lose power?          

David, <<   We're removing a plug to uncover the jet below it.>>  Yes, #10 on   the diagram is the plug (11mm) that you pull to get to the jet.

   

   The jet unscrews, comes out, has a little hole in it.  You plug that   somehow..(weld, JB, etc.).  Then reinsert the jet and reinstall the 11mm   plug.  

   

   My engine ran much better after the mod with no noted lag in acceleration.

   

   Eddie

   

   

   

   --- On Sat, 12/20/08, DAVID STROUD <dstroud(at)storm.ca>   wrote:   

From: DAVID STROUD   <dstroud(at)storm.ca>

   Subject: Re: Re: Why would my Yak 52 m14p lose power?

   To: m14pengines-list(at)matronics.com

   Date: Saturday, December 20, 2008, 10:32 AM         

I'm   slightly confused now. We're removing a plug to uncover the jet below it.   Your last sentence says    'plug it and reinstall' , do you   mean to    

      

remove the   jet, plug it ( the jet ) somehow, then reinstall the plugged jet and cover it   with the first plug? Is this process done on the Huosai    

      

engine too   ? thanks..   

      

    

      

David   Stroud     Ottawa, Canada

   Christavia C-FDWS

   Fairchild 51 replica

   under  construction C-FYXV   

    	  Quote: 	
		        

-----   Original Message -----    

      

From: Eddie Moran (eddiemoranii(at)yahoo.com)    

      

To: m14pengines-list(at)matronics.com (m14pengines-list(at)matronics.com)    

      

Sent: Saturday, December   20, 2008 10:02 AM   

      

Subject: Fw: Re:   Why would my Yak 52 m14p lose power?   

      

    

                  	  Quote: 	
		                                              

Mark,        

       

       I am       not an expert by any means but I agree on the ice theory.  I also       have a picture of the accel plug fix.  I would plug that if you have       not already.  The following info came from Dennis a few years ago.

       

       

       

       See       attached.  Item #10 is a plug (11 mm I believe) and under the plug       is the acceleration pump jet.  The jet has a slot in it just like a       slotted screw.  Use a straight blade screwdriver to remove.  Plug it and reinstall.

       

       The figure is attached.

       

       Eddie Moran

       N320VT 

       Murphy Moose

       

       --- On Thu, 12/18/08, markgreenway <geewhizmark(at)gmail.com>       wrote:       

From: markgreenway <geewhizmark(at)gmail.com>

       Subject: Why would my Yak 52 m14p lose power?

       To: m14pengines-list(at)matronics.com

       Date: Thursday, December 18, 2008, 9:30 PM        	  Quote: 	
		  --> M14PEngines-List message posted by: "markgreenway"

<geewhizmark(at)gmail.com>

      

Hello Guys

      

    Any idea why I lost power and had to make a forced landing ,because when

crossing midfield for landing, the motor lost power when I

 throttled back. It

never totally died and it regained power once on the ground

      

      	


       

                       

                

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       [quote][b]

dsavarese0812(at)bellsout
Guest

Posted: Mon Dec 22, 2008 4:16 am Post subject: Why would my Yak 52 m14p lose power?

I acquired the "fix" from our friend George  Coy.

  

 All good input Mark.  I also agree one can  pull the throttle back until one can see a slight decrease in MP and save  fuel.  This is proven by watching the JPI fuel flow instrument installed in  my airplane as well as others.

  

 Dennis

  

 [quote]   ---

n395v

Joined: 10 Jan 2006
Posts: 450

Posted: Mon Dec 22, 2008 5:12 am Post subject: Re: Why would my Yak 52 m14p lose power?

Is not a slight stumble inherent in all radials?

_________________
Milt

KJKimball(at)aol.com
Guest

Posted: Mon Dec 22, 2008 6:39 am Post subject: Why would my Yak 52 m14p lose power?

The carb mod was the original idea of Ben Morphew of McKinney Texas in 1990  to stop the stubble the engine has when advancing the throttle.  Ben was  part of a group with Dr Tom ?? who brought in several yak 52s and 3 sukhois in  1990.  These airplanes all had M14P engines not PF engines since the PF was  not available until the late 90's. So, the talk of it only being a PF issue  cannot be correct.  Ben has lots of experience with PS5 pressure carbs on  Pitts airplanes and knew of a mod made on those PS5 carbs.  This PS5 mod  was done by Curtis Pitts and the carb OH facility in FL that Curtis  used for his 4 cyl lyc. airplanes since the PS5 was designed for engines of more  than 400 cubic inches.  On the PS5, the accelerator pump diaphragm was  limited in travel with a bolt.  

  

 In the M14 carb, there is no accelerator pump diaphragm instead having an  over enrichment jet.  Ben studied the carb data and determined which jet to  plug up.  Ben made the mod on Les Crowder's yak (Ben and Les were  neighbors and friends) as a test of his theory and it worked great!  So,  they began to do the mod to other airplanes since Ben and Les were seeing  airplanes damaged with hard landings and taxi problems due to the blubber of the  carb.  Les did Yaks and Ben did Sukhois. In 1997, Ben showed me the mod on  an engine here and recommended we do this mod to all the M14 engine we mess with  which we have done.  I then created the "how-to" instructions on our  website.  Again, this blubber can happen with P engines not just PF and  this is shown to be true based on the history and time line of the carb  mod.

  

 Can you solve the throttle stumble in other ways?  Sure.  Now we  know there are a handful of jets available for this port which can be swapped  around you get better performance but it make take several trials to get it  right.  The carb mod is simple to do, takes only minutes and is  reversible.  Folks in the non-south can have 2 jets, one plugged for warm  and one unplugged for cold flying as George Coy later pointed out that the mod  works great with the exception of some airplanes operated in extreme cold  conditions.  The over enrichment jet helps to keep the very cold engine  running at lower power.

  

 As for carb ice on pressure carbs, it is possible and has been shown to  have happen on PS5 carbs and on the M14 carb.  I know of a suhkoi that had  ice and the owner was able to see the ice on inspection.  I know of a yak  52 in the northwest that had ice on taxi and warm up to the point it locked the  throttle in position.  Once shut down and the engine heat warmed the carb  body, the ice melted and the throttle operated normally.  It can happen in  the right conditions.

  

 Have Fun,

  

 Kevin Kimball

  

 .  



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yakplt(at)yahoo.com
Guest

Posted: Mon Dec 22, 2008 8:53 am Post subject: Why would my Yak 52 m14p lose power?

Thanks for the really informative reply Kevin, and I stand corrected.  You really raised my eyebrows when you mentioned Les.  My YAK-50 used to be owned by Les.  It is possible that my carb has been modded and I never even knew it, which would sure refute what I said about every P model running so well wouldn't it?  I am going to pull that jet and take a look at it today.  well..... maybe tomorrow!    

  

 Thanks again for presenting the facts, and Dennis, looks like you were right as well  when you mentioned it did not start with the PF but with the P's.  Anyway, I stand corrected and am happy to say so.  

  

 Now, back to the gent with the original problem.  Did his engine stumble when he pushed the power up, or did the engine die when he pulled it back to idle?  

  

 Mark Bitterlich

  

  

 

 

 

   From: "KJKimball(at)aol.com" <KJKimball(at)aol.com>

To: m14pengines-list(at)matronics.com

Sent: Monday, December 22, 2008 6:38:18 AM

Subject: Re: Why would my Yak 52 m14p lose power?



 The carb mod was the original idea of Ben Morphew of McKinney Texas in 1990 to stop the stubble the engine has when advancing the throttle.  Ben was part of a group with Dr Tom ?? who brought in several yak 52s and 3 sukhois in 1990.  These airplanes all had M14P engines not PF engines since the PF was not available until the late 90's. So, the talk of it only being a PF issue cannot be correct.  Ben has lots of experience with PS5 pressure carbs on Pitts airplanes and knew of a mod made on those PS5 carbs.  This PS5 mod was done by Curtis Pitts and the carb OH facility in FL that Curtis used for his 4 cyl lyc. airplanes since the PS5 was designed for engines of more than 400 cubic inches.  On the PS5, the accelerator pump diaphragm was limited in travel with a bolt.  

  

 In the M14 carb, there is no accelerator pump diaphragm instead having an over enrichment jet.  Ben studied the carb data and determined which jet to plug up.  Ben made the mod on Les Crowder's yak (Ben and Les were neighbors and friends) as a test of his theory and it worked great!  So, they began to do the mod to other airplanes since Ben and Les were seeing airplanes damaged with hard landings and taxi problems due to the blubber of the carb.  Les did Yaks and Ben did Sukhois. In 1997, Ben showed me the mod on an engine here and recommended we do this mod to all the M14 engine we mess with which we have done.  I then created the "how-to" instructions on our website.  Again, this blubber can happen with P engines not just PF and this is shown to be true based on the history and time line of the carb mod.

  

 Can you solve the throttle stumble in other ways?  Sure.  Now we know there are a handful of jets available for this port which can be swapped around you get better performance but it make take several trials to get it right.  The carb mod is simple to do, takes only minutes and is reversible.  Folks in the non-south can have 2 jets, one plugged for warm and one unplugged for cold flying as George Coy later pointed out that the mod works great with the exception of some airplanes operated in extreme cold conditions.  The over enrichment jet helps to keep the very cold engine running at lower power.

  

 As for carb ice on pressure carbs, it is possible and has been shown to have happen on PS5 carbs and on the M14 carb.  I know of a suhkoi that had ice and the owner was able to see the ice on inspection.  I know of a yak 52 in the northwest that had ice on taxi and warm up to the point it locked the throttle in position.  Once shut down and the engine heat warmed the carb body, the ice melted and the throttle operated normally.  It can happen in the right conditions.

  

 Have Fun,

  

 Kevin Kimball

  

 .  



    [/b][b]

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