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engine running rough

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ariekert(at)t-online.de
Guest

Posted: Tue Aug 16, 2011 11:05 pm Post subject: engine running rough

Good morning,  

   

I discovered my engine (M14P) showing the following characteristic:  

   

It’s not the smoothest engine I’ve seen but running ok from start. Then I fly for some 30 minutes, have a break and when I go flying again, the engine runs with quite more vibrations than before. It’s not the frequent shakes that I remember from an engine with a magneto coil turning bad. It’s just running evenly with noticeable more vibes than the flight before which develops through the complete RPM range with peaks at certain RPM. This behaviour is shown consistently every flying day.  

   

So far I checked the mag timing being at 15.5 BTDC and synchronous, the breaker gaps are correct, the plugs gaps are correct and the plugs tested.  

   

Any ideas where to look now? All recommendations will be greatly appreciated.  

   

Cheers,  

Armin  

       [quote][b]

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CD 2.0

Joined: 21 Feb 2011
Posts: 43

Posted: Wed Aug 17, 2011 12:49 am Post subject: Re: engine running rough

Armin, 



Try to pay particular attention to determine it is "engine roughness or vibration"... particularly when there are no engine instruments indicating trouble.  Roughness comes and goes whereas vibration is steady but may change or go away at a different rpm setting.  



What type/brand of spark plugs are you using? 



Check for ignition lead misfire too... this can be caused by a faulty lead, faulty connection at spark plug, or electrode pin not making contact with conductor causing terminal well flashover. 



Did you just fixed a magneto coil problem?.... When magneto coils go bad, they usually break down when hot... the engine runs smoothly until a half hour into flight before it gets rough... the next day, when the coil has cooled down, the engine operates fine. The magneto will test fine on a test bench. 



Propeller out of track or unbalanced?... out of balance propellers or harmonic engine vibrations often result in cracks in spinners and engine baffling.



Also an intake leak could cause some roughness at high throttle settings because the cylinders nearer to the leak might be getting less fuel air mix than those further away.  It doesn't take leaks in each intake pipe to ruin combustion. A large enough leak in one place can ruin combustion in all the cylinders.



Carl



 	  ariekert(at)t-online.de wrote: 	
		  Good morning,  

   

I discovered my engine (M14P) showing the following characteristic:  

   

It’s not the smoothest engine I’ve seen but running ok from start. Then I fly for some 30 minutes, have a break and when I go flying again, the engine runs with quite more vibrations than before. It’s not the frequent shakes that I remember from an engine with a magneto coil turning bad. It’s just running evenly with noticeable more vibes than the flight before which develops through the complete RPM range with peaks at certain RPM. This behaviour is shown consistently every flying day.  

   

So far I checked the mag timing being at 15.5 BTDC and synchronous, the breaker gaps are correct, the plugs gaps are correct and the plugs tested.  

   

Any ideas where to look now? All recommendations will be greatly appreciated.  

   

Cheers,  

Armin

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dsavarese0812(at)bellsout
Guest

Posted: Wed Aug 17, 2011 9:12 am Post subject: engine running rough

Also take a look at the rubber engine mount bushings. If deteriorated as 

evidence of cracking around the exposed part, (the part you can see 

easily) they need to be replaced. As with any aircraft engine, bad 

engine mount rubber bushings will definitely contribute to engine 

vibrations.

Dennis

A. Dennis Savarese

334-285-6263

334-546-8182 (cell)

Skype: Yakguy1

www.yak-52.com

On 8/17/2011 3:49 AM, CD 2.0 wrote:

 	  Quote: 	

 Armin,

 Try to pay particular attention to determine it is "engine roughness or vibration"... particularly when there are no engine instruments indicating trouble.  Roughness comes and goes whereas vibration is steady but may change or go away at a different rpm setting.

 What type/brand of spark plugs are you using?

 Check for ignition lead misfire too... this can be caused by a faulty lead, faulty connection at spark plug, or electrode pin not making contact with conductor causing terminal well flashover.

 Did you just fixed a magneto coil problem?.... When magneto coils go bad, they usually break down when hot... the engine runs smoothly until a half hour into flight before it gets rough... the next day, when the coil has cooled down, the engine operates fine. The magneto will test fine on a test bench.

 Propeller out of track or unbalanced?... out of balance propellers or harmonic engine vibrations often result in cracks in spinners and engine baffling.

 Also an intake leak could cause some roughness at high throttle settings because the cylinders nearer to the leak might be getting less fuel air mix than those further away.  It doesn't take leaks in each intake pipe to ruin combustion. A large enough leak in one place can ruin combustion in all the cylinders.

 Carl

 ariekert(at)t-online.de wrote:

> Good morning,

>

> I discovered my engine (M14P) showing the following characteristic:

>

> It’s not the smoothest engine I’ve seen but running ok from start. Then I fly for some 30 minutes, have a break and when I go flying again, the engine runs with quite more vibrations than before. It’s not the frequent shakes that I remember from an engine with a magneto coil turning bad. It’s just running evenly with noticeable more vibes than the flight before which develops through the complete RPM range with peaks at certain RPM. This behaviour is shown consistently every flying day.

>

> So far I checked the mag timing being at 15.5 BTDC and synchronous, the breaker gaps are correct, the plugs gaps are correct and the plugs tested.

>

> Any ideas where to look now? All recommendations will be greatly appreciated.

>

> Cheers,

> Armin

>

 Read this topic online here:

 http://forums.matronics.com/viewtopic.php?p=349729#349729

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javiercarrascob

Joined: 06 Sep 2009
Posts: 62
Location: Virginia

Posted: Wed Aug 17, 2011 8:08 pm Post subject: engine running rough

Do you have a autoplug convertion?

  

 If not try that, I had a similar issue specially in hot days, try to keep the cyl heat temp close to 180C and don't let it cool down as when you dive for landin during a few minuts at low settings play with the shoutter to keep the temps around 170 180.

  

 Hope that helps.

  

 JC



--- On Wed, 8/17/11, Armin Riekert <ariekert(at)t-online.de> wrote:



  	  Quote: 	
		  

From: Armin Riekert <ariekert(at)t-online.de>

Subject: engine running rough

To: yak-list(at)matronics.com

Date: Wednesday, August 17, 2011, 3:02 AM



       

Good morning,

 

 

 

I discovered my engine (M14P) showing the following characteristic:

 

 

 

It’s not the smoothest engine I’ve seen but running ok from start. Then I fly for some 30 minutes, have a break and when I go flying again, the engine runs with quite more vibrations than before. It’s not the frequent shakes that I remember from an engine with a magneto coil turning bad. It’s just running evenly with noticeable more vibes than the flight before which develops through the complete RPM range with peaks at certain RPM. This behaviour is shown consistently every flying day.

 

 

 

So far I checked the mag timing being at 15.5 BTDC and synchronous, the breaker gaps are correct, the plugs gaps are correct and the plugs tested.

 

 

 

Any ideas where to look now? All recommendations will be greatly appreciated.

 

 

 

Cheers,

 

Armin



 	  Quote: 	
		  



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