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Engine hesitates when advancing throttle

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eddiemoranii(at)yahoo.com
Guest

Posted: Fri Jun 22, 2007 7:29 am Post subject: Engine hesitates when advancing throttle

Hi, 

   

  I have a M14 installed in my Murphy Moose.  The engine runs great and I have flown the aircraft already.  

   

  Here is my situation.  I have a Vernier throttle cable installed directly to a fabricated throttle arm.  We had determined that the original "arm" was too short and gave us a very small throw with the direct cable.  

   

  While doing the "high speed" taxi tests I noted a strong hesitation while advancing the throttle.  The hesitation or "burp" accured right during the initial throttle application.  It was short but "disturbing".  The engine then picked back up and accelerated rapidly to full power.

   

  I have done the throttle movement just using the "twist the blue knob" on the Vernier cable and the acceleration is what you would expect by pushing in a "normal" throttle.  It only takes a few twists,  say 4 or 5 to get a lot of engine response.

   

  I have inspected the carb for any loose or missing plugs or any anomalies.  There were none.

   

  The air filter and air box are all OK.

   

  I am thinking that the throttle arm on the carb might be a bit short creating a "too small" of a throw when the throttle is "pushed in".  Does this sound like a likely fix?

   

  Any other ideas or previous experience with this problem?

   

  Eddie Moran

   

   



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BPA(at)bpaengines.com
Guest

Posted: Fri Jun 22, 2007 8:35 am Post subject: Engine hesitates when advancing throttle

Just a thought, but would it be possible that when advancing the throttle that the cable my have a little bit of deflection causing the arm to not move immediately and then suddenly advances?  

   

Allen Barrett  

BPE, Inc.   

   

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dsavarese(at)elmore.rr.co
Guest

Posted: Fri Jun 22, 2007 8:57 am Post subject: Engine hesitates when advancing throttle

Eddie,

 The problem you've described is quite common on the M14P,  particularly in hot weather.  It is related to the acceleration pump and  its associated jet.  There is a set of jets that originally was used to  "adjust" the fuel flow when advancing the throttle.  But the set of jets is  now extremely difficult to find.  A solution we now use is to literally  plug the acceleration pump jet and reinstall it.  It will definitely cure  the hesitation problem which of course, get's your attention when you're on  short final and you advance the throttle a little bit.  Some people solder  the hole in the jet closed.  Others have fabricated a screw-in plug.   I have used JB Weld epoxy and let it cure overnight.  It also works quite  well.

 Dennis

  

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george(at)gesoco.com
Guest

Posted: Fri Jun 22, 2007 10:51 am Post subject: Engine hesitates when advancing throttle

As others have said it is normal. It can be cured by gentle  initial application of the throttle from idle. More important is when you have  closed the throttle in the air to descend. Here you need to "clear the throttle"  every 20 to 30 seconds. and better yet train yourself to recognize  "zero  Thrust" feeling and use it on the short final when you need it. I have always  carried a little throttle until well into the round-out and flair. This is a 621  cu inch engine and with the throttle closed it is a great dynamic brake.  

 George



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

Sent: Friday, June 22, 2007 11:30 AM

To:  m14pengines-list(at)matronics.com

Subject: Engine  hesitates when advancing throttle 

 

 Hi, 

  

 I have a M14 installed in my Murphy Moose.  The engine runs great and  I have flown the aircraft already.  

  

 Here is my situation.  I have a Vernier throttle cable installed  directly to a fabricated throttle arm.  We had determined that the original  "arm" was too short and gave us a very small throw with the direct cable.   

  

 While doing the "high speed" taxi tests I noted a strong hesitation while  advancing the throttle.  The hesitation or "burp" accured right during the  initial throttle application.  It was short but "disturbing".  The  engine then picked back up and accelerated rapidly to full power.

  

 I have done the throttle movement just using the "twist the blue knob" on  the Vernier cable and the acceleration is what you would expect by pushing in a  "normal" throttle.  It only takes a few twists, say 4 or 5 to get a lot of  engine response.

  

 I have inspected the carb for any loose or missing plugs or any  anomalies.  There were none.

  

 The air filter and air box are all OK.

  

 I am thinking that the throttle arm on the carb might be a bit short  creating a "too small" of a throw when the throttle is "pushed in".  Does  this sound like a likely fix?

  

 Any other ideas or previous experience with this problem?

  

 Eddie Moran

  

  

 

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PeteAbbott(at)aol.com
Guest

Posted: Fri Jun 22, 2007 11:54 am Post subject: Engine hesitates when advancing throttle

A question for Dennis regarding his answer to this question.

  

 Is it a problem with the engine running lean or rich?  In the old  days, when I was a hot rodder, we had accelerator pumps, when you gave there  full throttle and the quads opened up the engine would hastate do to running  lean. The exc pump would inject raw fuel into the intake and prevent this  hesitation.

  

 I admit that I have never been inside my Yak 52 carb so I really do not  know how it works. Please enlighten me.

  

 Thanks

  

 Pete

  

 N852GC



See what's free at AOL.com. 

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culpspecial(at)yahoo.com
Guest

Posted: Fri Jun 22, 2007 12:00 pm Post subject: Engine hesitates when advancing throttle

Our Sukoi was doing that back in 1991.  Les Crowder told me to weld the jet up redrill smaller.  Then Ben Morfue studied the manual and said to just weld the ****** up and I have been doing that every since on quite a few M-14Ps and it has always taken the studder out of them.  

  The second thing that has been funny over the years is not many people adjust the carbs and the mixture adjustment on the lower right needs to be adjusted after the first few hours.  Most M-14Ps mixture covers are still factory sealed with the factory safety wire and tag on the cover.

  Pretty easy to adjust.  Just have someone in the plane and adjust at low and intermediate rpms.

  Steve Culp



BPA <BPA(at)bpaengines.com> wrote:

  [quote]              Just a thought, but would it be possible that when advancing the throttle that the cable my have a little bit of deflection causing the arm to not move immediately and then suddenly advances?

   

  Allen Barrett

  BPE, Inc. 

   

  --

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eddiemoranii(at)yahoo.com
Guest

Posted: Fri Jun 22, 2007 3:18 pm Post subject: Engine hesitates when advancing throttle

Well, I have decided.  When I get home I am going to weld the little ******.  

   

  Thanks to all who helped.

   

  Eddie

  



Steve Culp <culpspecial(at)yahoo.com> wrote:

  [quote]  Our Sukoi was doing that back in 1991.  Les Crowder told me to weld the jet up redrill smaller.  Then Ben Morfue studied the manual and said to just weld the ****** up and I have been doing that every since on quite a few M-14Ps and it has always taken the studder out of them.  

  The second thing that has been funny over the years is not many people adjust the carbs and the mixture adjustment on the lower right  needs to be adjusted after the first few hours.  Most M-14Ps mixture covers are still factory sealed with the factory safety wire and tag on the cover.

  Pretty easy to adjust.  Just have someone in the plane and adjust at low and intermediate rpms.

  Steve Culp



BPA <BPA(at)bpaengines.com> wrote:

  [quote]              Just a thought, but would it be possible that when advancing the throttle that the cable my have a little bit of deflection causing the arm to not move immediately and then suddenly advances?

   

  Allen Barrett

  BPE, Inc. 

   

  --

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eddiemoranii(at)yahoo.com
Guest

Posted: Wed Jun 27, 2007 10:31 am Post subject: Engine hesitates when advancing throttle

To all,

   

  JB Weld on the accelerator jet and all is well.  Thanks to all that suggested fixes.

   

  Eddie Moran



Steve Culp <culpspecial(at)yahoo.com> wrote:

  [quote]  Our Sukoi was doing that back in 1991.  Les Crowder told me to weld the jet up redrill smaller.  Then Ben Morfue studied the manual and said to just weld the ****** up and I have been doing that every since on quite a few M-14Ps and it has always taken the studder out of them.  

  The second thing that has been funny over the years is not many people adjust the carbs and the mixture adjustment on the lower right needs to be adjusted after the first few hours.  Most M-14Ps mixture covers are still factory sealed with the factory safety wire and tag on the  cover.

  Pretty easy to adjust.  Just have someone in the plane and adjust at low and intermediate rpms.

  Steve Culp



BPA <BPA(at)bpaengines.com> wrote:

  [quote]              Just a thought, but would it be possible that when advancing the throttle that the cable my have a little bit of deflection causing the arm to not move immediately and then suddenly advances?

   

  Allen Barrett

  BPE, Inc. 

   

  --

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dstroud(at)storm.ca
Guest

Posted: Wed Jun 27, 2007 5:33 pm Post subject: Engine hesitates when advancing throttle

Good for you Eddie....( hockey28, eh?...No Sens  no..

  

 But..does anyone know if the same affliction / cure is  applicable

 to the Huosai engine/carb? Thanks..

  

 David Stroud   Ottawa, Canada

C-FDWS  Christavia  

Fairchild 51 under construction

and on the gear...



 [quote]   ---

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