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Engine roughness

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hgmckay

Joined: 23 May 2006
Posts: 397

Posted: Tue Aug 10, 2010 12:48 pm Post subject: Engine roughness

I need some help and advice. I was mechanically  adjusting my carbs yesterday, and in the process I thought I would check the  position of the Idle Mixture screw on the bottom of the carbs. I ran the screws  in fully closed, and then backed them out the 1.5 turns as recommended by Rotax.  The engine now runs rough at idle, and in the operating range up to 3000 rpm.  You can feel it. I did not increase the speed beyond 3000 rpm for fear of harm  to the engine.  Unfortunately I did not count the number of turns it took  to close the Idle Mixture Screws, so I don't know if they were set at 1.5 turns  (counterclockwise) initially. I have not pneumatically checked the balance. What  are some of the conditions that can cause this type rough engine  operation?

  

 Hugh McKay

 Allegro 2000

 Rotax 912 UL



   [quote][b]

Roger Lee

Joined: 10 Jan 2006
Posts: 1464
Location: Tucson, Az.

Posted: Tue Aug 10, 2010 12:54 pm Post subject: Re: Engine roughness

Hi Hugh,



Those mixture screws should be set before a pneumatic balance. Since you now have those set you absolutely need to do a pneumatic balance. Leave the screws at 1.5 turns out. The roughness is because they are helping with the mixture at the low rpms. As you go above 3500 rpm to 4000+rpm that circuit now longer is in play. After the pneumatic balance I would bet your engine will be smooth.

_________________
Roger Lee
Tucson, Az.
Rotax Instructor & Rotax IRC
Light Sport Repairman
Home 520-574-1080 TRY HOME FIRST
Cell 520-349-7056

hgmckay

Joined: 23 May 2006
Posts: 397

Posted: Thu Aug 12, 2010 5:00 pm Post subject: Engine roughness

Roger,etal



Well, in the course of balancing my carbs a friend of mine ask me to check 

to make sure nothing was coming in contact with the pick-ups for the 

ignition circuits. All were fine except one. On my Allegro one of the 

cooling pipes drops down vertically near the back of the engine. This 

aluminum pipe was barely touching the pick-up for what I believe to be 

ignition circuit B. On page 121 in the Lockwood Aviation Supply Catalogue 

the pick-up I am referring to is the one shown as number 3. I assume the 

wiring diagram as shown is as if you are looking at the back of the engine. 

I corrected the position of the aluminum pipe so it cleared the pick-up an 

finished balancing the carbs. I noticed one of the small wires on the 

pick-up looked like it had the insulation worn off in one spot. I took a 

small amount of silicone and covered the spot. After finishing everything I 

decided to test fly the plane. During the normal starting procedure 

everything went fine and I taxied to the hold point. At the hold point I was 

going through the normal checks, one of which is an ignition check (i.e. I 

ran the engine up to 4000 rpm and killed one switch. The rpm drop was 

normal. When I killed the other switch the engine immediately shut off. I 

quickly opened the switch and the engine caught an ran fine. This alarmed me 

so I backed the engine down, revved it back up to 4000 rpm and the same thin 

happened. I began to taxi back to the hanger, but decided to try the circuit 

again. This time everything was normal. I did this three or four times and 

everything was normal so I decided to fly.



I flew around the "patch" for about 30 minutes with no problem, so came back 

an landed. I decided to fly one more pattern, but I though I would check the 

ignition circuits again. This time when I "killed" the first circuit all was 

fine. But when I "killed" the second one it failed again and shut the engine 

down. This time I took it to the hanger. Help!!!!!!



Hugh McKay

Allegro 2000 ELSA

Rotax 912 UL



--------------------------------------------------

From: "Roger Lee" <ssadiver1(at)yahoo.com>

Sent: Tuesday, August 10, 2010 4:54 PM

To: <rotaxengines-list(at)matronics.com>

Subject: Re: Engine roughness



 	  Quote: 	
		   



 Hi Hugh,



 Those mixture screws should be set before a pneumatic balance. Since you 

 now have those set you absolutely need to do a pneumatic balance. Leave 

 the screws at 1.5 turns out. The roughness is because they are helping 

 with the mixture at the low rpms. As you go above 3500 rpm to 4000+rpm 

 that circuit now longer is in play. After the pneumatic balance I would 

 bet your engine will be smooth.



 --------

 Roger Lee

 Tucson, Az.

 Light Sport Repairman - Maintenance Rated

 Rotax Repair Center

 520-574-1080





 Read this topic online here:



 http://forums.matronics.com/viewtopic.php?p=308271#308271

Thom Riddle

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

Posted: Fri Aug 13, 2010 2:20 am Post subject: Re: Engine roughness

Hugh,



A mag not firing is far more likely to be a wiring or switch fault than a faulty mag, also cheaper to remedy. I would start looking at the magneto switches first. If the connections are clean and secure, these generally fail before other components since they are mechanical and are switched off an on at least twice every flight. Randomly occurring faults are a hit-and-miss proposition when looking for them so if the switch seems okay, check out every inch of the wiring to/from that switch.



Keep us posted on what you find.

_________________
Thom Riddle
Buffalo, NY (9G0)

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

hgmckay

Joined: 23 May 2006
Posts: 397

Posted: Fri Aug 13, 2010 4:32 am Post subject: Engine roughness

Thom/Dick,



Ok, I understand what you are telling me to do, and I will. However, being 

an engineer (civil, not electrical) my brain is asking what is causing  the 

engine to cut off when I turn off the one mag? If the wire is broke in the 

first place, what does turning the switch off have to do with shutting the 

engine down? I am confused (which may be normal in my case)!



Hugh



--------------------------------------------------

From: "Thom Riddle" <riddletr(at)gmail.com>

Sent: Friday, August 13, 2010 6:20 AM

To: <rotaxengines-list(at)matronics.com>

Subject: Re: Engine roughness



 	  Quote: 	
		   

 <riddletr(at)gmail.com>



 Hugh,



 A mag not firing is far more likely to be a wiring or switch fault than a 

 faulty mag, also cheaper to remedy. I would start looking at the magneto 

 switches first. If the connections are clean and secure, these generally 

 fail before other components since they are mechanical and are switched 

 off an on at least twice every flight. Randomly occurring faults are a 

 hit-and-miss proposition when looking for them so if the switch seems 

 okay, check out every inch of the wiring to/from that switch.



 Keep us posted on what you find.



 --------

 Thom Riddle

 Buffalo, NY (9G0)

 Kolb Slingshot SS-021

 Jabiru 2200A #1574

 Tennessee Prop 64x32

 The truth will set you free. But first, it will piss you off.

 - Gloria Steinem





 Read this topic online here:



 http://forums.matronics.com/viewtopic.php?p=308626#308626

Thom Riddle

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

Posted: Fri Aug 13, 2010 4:55 am Post subject: Re: Engine roughness

Hugh,



Magnetos that are working correctly, are functional UNLESS the the "P-Lead" is GROUNDED. When you turn the mag switch to the OFF position, that grounds the mag so it will not function. If the mag is inadvertently grounded without turning the mag switch to OFF, then it will not work. So essentially, you are looking for an inadvertent grounding of the mag that "fails" when you check them during the run-up.



The fact that mags function unless grounded is why it is important to check the mag off switch for proper functioning during pre-take-off check. Your check for rpm drop is important but also making sure the switch does ground the mag is a safety issue too. If the switch does not ground the mag, it is always hot.

_________________
Thom Riddle
Buffalo, NY (9G0)

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

hgmckay

Joined: 23 May 2006
Posts: 397

Posted: Fri Aug 13, 2010 5:38 am Post subject: Engine roughness

Thom,



My head is probably really thick on this one. I still do not understand what 

would cause the engine to completely cut off if there is a break in the wire 

on that mag when the mag switch is turned off. I there is a break in the 

wire between the switch and the engine anyway, what does activating or 

de-activating the switch have to do with it?



Hugh



--------------------------------------------------

From: "Thom Riddle" <riddletr(at)gmail.com>

Sent: Friday, August 13, 2010 8:55 AM

To: <rotaxengines-list(at)matronics.com>

Subject: Re: Engine roughness



 	  Quote: 	
		   

 <riddletr(at)gmail.com>



 Hugh,



 Magnetos that are working correctly, are functional UNLESS the the 

 "P-Lead" is GROUNDED. When you turn the mag switch to the OFF position, 

 that grounds the mag so it will not function. If the mag is inadvertently 

 grounded without turning the mag switch to OFF, then it will not work. So 

 essentially, you are looking for an inadvertent grounding of the mag that 

 "fails" when you check them during the run-up.



 The fact that mags function unless grounded is why it is important to 

 check the mag off switch for proper functioning during pre-take-off check. 

 Your check for rpm drop is important but also making sure the switch does 

 ground the mag is a safety issue too. If the switch does not ground the 

 mag, it is always hot.



 --------

 Thom Riddle

 Buffalo, NY (9G0)

 Kolb Slingshot SS-021

 Jabiru 2200A #1574

 Tennessee Prop 64x32

 The truth will set you free. But first, it will piss you off.

 - Gloria Steinem





 Read this topic online here:



 http://forums.matronics.com/viewtopic.php?p=308646#308646

Thom Riddle

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

Posted: Fri Aug 13, 2010 5:56 am Post subject: Re: Engine roughness

Hugh,



When you turn off the Left mag switch (for example), that action should ground the Left mag (disabling it), thus leaving the engine running on the Right mag only. If you turn off the Left mag and the engine quits, it means that the Right mag is not firing the engine. This means that one (or combination) of the following things is happening:

1) Right mag is faulty.

2) Right mag is grounded.



The Right mag being inadvertently grounded could be caused by one of two things, that I can think of:

A) A bad switch (mistakenly grounding the mag when the switch is in the on position), unlikely but possible.

B) Right mag wire has made ground elsewhere, most likely.



So, what you are looking for is these two things. If you find no fault in either of these, then you need to look deeper, i.e., check out the functioning of the mag itself. That is beyond the scope of my ability to explain in an email.



I hope this helps.

_________________
Thom Riddle
Buffalo, NY (9G0)

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

sdemeyer

Joined: 31 Jul 2009
Posts: 45

Posted: Fri Aug 13, 2010 7:13 am Post subject: Engine roughness

I have had this broken wire problem too, several times with exactly the same symptoms. The faulty wire(s) in my case was the one coming from the stator assembly and was broken just before the module connector.



Scott



--- On Fri, 8/13/10, Thom Riddle <riddletr(at)gmail.com> wrote:

[quote]

From: Thom Riddle <riddletr(at)gmail.com>

Subject: Re: Engine roughness

To: rotaxengines-list(at)matronics.com

Date: Friday, August 13, 2010, 6:56 AM



--> RotaxEngines-List message posted by: "Thom Riddle" <[url=/mc/compose?to=riddletr(at)gmail.com]riddletr(at)gmail.com[/url]>



Hugh,



When you turn off the Left mag switch (for example), that  action should ground the Left mag (disabling it), thus leaving the engine running on the Right mag only. If you turn off the Left mag and the engine quits, it means that the Right mag is not firing the engine. This means that one (or combination) of the following things is happening:

1) Right mag is faulty.

2) Right mag is grounded.



The Right mag being inadvertently grounded could be caused by one of two things, that I can think of:

A) A bad switch (mistakenly grounding the mag when the switch is in the on position), unlikely but possible.

B) Right mag wire has made ground elsewhere, most likely.



So, what you are looking for is these two things. If you find no fault in either of these, then you need to look deeper, i.e., check out the functioning of the mag itself. That is beyond the scope of my ability to explain in an email.



I hope this helps.



--------

Thom Riddle

Buffalo, NY (9G0)

Kolb Slingshot  SS-021

Jabiru 2200A #1574

Tennessee Prop 64x32

The truth will set you free. But first, it will piss you off.

 - Gloria Steinem





Read this topic online here:



http://forums.matronics.com/viewtopic.php?p=308657#308657



 [quote][b]

jonathan(at)entry.co.za
Guest

Posted: Fri Aug 13, 2010 8:32 am Post subject: Engine roughness

Yep that is where I had the problem  too.

  

 Jonathan

 [quote]   ---

s.clive.richards(at)homec
Guest

Posted: Fri Aug 13, 2010 9:20 am Post subject: Engine roughness

Thom

               The break in the wire they are referring to is in a  Red 

power supply wire to the electronic module not the P lead which if grounded 

by mag switch or a short to ground turns that module off.

                               Clive

---

Thom Riddle

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

Posted: Fri Aug 13, 2010 9:46 am Post subject: Re: Engine roughness

Clive,



I never mentioned a broken wire, that was someone else. I was providing guidance to Hugh to help him find a possible source of the problem, beginning with the mag switches on to the mag grounding wires. I know an OPEN in a ground wire will not cause a mag to 'fail', but to remain hot. 



In any case, since the failure appears to be intermittent, it is likely to be a bad connection or partially broken wire if on the power side, or a "sometimes grounding" P-lead or p-lead switch wire.



Thom

http://sites.google.com/site/riddletr/a&pmechanix

_________________
Thom Riddle
Buffalo, NY (9G0)

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

sdemeyer

Joined: 31 Jul 2009
Posts: 45

Posted: Fri Aug 13, 2010 11:16 am Post subject: Re: Engine roughness

 	  Thom Riddle wrote: 	
		  Clive,



I never mentioned a broken wire, that was someone else. I was providing guidance to Hugh to help him find a possible source of the problem, beginning with the mag switches on to the mag grounding wires. I know an OPEN in a ground wire will not cause a mag to 'fail', but to remain hot. 



In any case, since the failure appears to be intermittent, it is likely to be a bad connection or partially broken wire if on the power side, or a "sometimes grounding" P-lead or p-lead switch wire.



Thom

http://sites.google.com/site/riddletr/a&pmechanix 	


Sorry Guys, there are two threads going on here with almost exactly the same subject. My reply was meant for the other thread!



Scott

s.clive.richards(at)homec
Guest

Posted: Fri Aug 13, 2010 12:22 pm Post subject: Engine roughness

Thom

                       Sorry this should have been addressed to Hugh in 

reply to his question included in my post I typed name at top of post 

instead of bottom.

do not archive

Clive-

--

rickofudall

Joined: 19 Sep 2009
Posts: 1392
Location: Udall, KS, USA

Posted: Fri Aug 13, 2010 3:35 pm Post subject: Engine roughness

Just a guess, but the wire is broken and the insulation is holding it such that it makes intermittent contact.



Rick Girard

LSARM # 3178721



On Fri, Aug 13, 2010 at 7:29 AM, Hugh McKay <hgmckay(at)bellsouth.net (hgmckay(at)bellsouth.net)> wrote:

 [quote]--> RotaxEngines-List message posted by: "Hugh McKay" <hgmckay(at)bellsouth.net (hgmckay(at)bellsouth.net)>

  

 Thom/Dick,

 

 Ok, I understand what you are telling me to do, and I will. However, being an engineer (civil, not electrical) my brain is asking what is causing  the engine to cut off when I turn off the one mag? If the wire is broke in the first place, what does turning the switch off have to do with shutting the engine down? I am confused (which may be normal in my case)!

  

 Hugh

 

 --------------------------------------------------

 From: "Thom Riddle" <riddletr(at)gmail.com (riddletr(at)gmail.com)>

 Sent: Friday, August 13, 2010 6:20 AM

 To: <rotaxengines-list(at)matronics.com (rotaxengines-list(at)matronics.com)>



 Subject: Re: Engine roughness

 

  	  Quote: 	
		   --> RotaxEngines-List message posted by: "Thom Riddle" <riddletr(at)gmail.com (riddletr(at)gmail.com)>

 

 Hugh,

 

 A mag not firing is far more likely to be a wiring or switch fault than a faulty mag, also cheaper to remedy. I would start looking at the magneto switches first. If the connections are clean and secure, these generally fail before other components since they are mechanical and are switched off an on at least twice every flight. Randomly occurring faults are a hit-and-miss proposition when looking for them so if the switch seems okay, check out every inch of the wiring to/from that switch.

  

 Keep us posted on what you find.

 

 --------

 Thom Riddle

 Buffalo, NY (9G0)

 Kolb Slingshot SS-021

 Jabiru 2200A #1574

 Tennessee Prop 64x32

 

 

 The truth will set you free. But first, it will piss you off.

 - Gloria Steinem

 

 

 

 



 Read this topic online here:

 

 

http://forums.matronics.com/viewtopic.php?p=308626#308626

 

 

 

 

 

 

 

 

 

 

 	
 

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