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Daul Mags on the 914

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Alan Carter

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

Posted: Wed Jun 19, 2013 1:45 pm Post subject: Daul Mags on the 914

Hello All.

I have just replace a mag HT coil on my 914, simple job, but a ridiculous job to do it took my a day because you can not get at the nuts and bolts.

However all is well now, I have equal drops of about 280to300 on each .

I can understand the more efficient burning on two hence the extra 300 rpm.

But when run on either the left or right mag the engine is not as smooth as when on two. WHY??

A car has only one set of plugs and that runs smooth,  So at 4000rpm on two smooth 3710 rpms on one not as smooth ??



Alan

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BARRY CHECK 6

Joined: 15 Mar 2011
Posts: 738

Posted: Wed Jun 19, 2013 3:08 pm Post subject: Daul Mags on the 914

Alen:



The simple answers are:

When you adjust the carb it is adjusted for the spark available.  If you had only one spark plug you would adjust the carb for the best run with that one plug.  Since you have two spark plugs the burn is better - BUT - You need the two plugs. 
Spark Plug Location - When you are talking real estate there are three things that matter - Location - Location - Location.  When running on ONE plug in a dual plug system, it is NOT in the best location to give the best spark/burn.  A car puts the plug in the optimum location for spark and burn.  
Most aircraft engines sacrifice spark plug location for Safety/REDUNDANCY.    

Barry

On Wed, Jun 19, 2013 at 5:45 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)>

  

 Hello All.

 I have just replace a mag HT coil on my 914, simple job, but a ridiculous job to do it took my a day because you can not get at the nuts and bolts.

 However all is well now, I have equal drops of about 280to300 on each .

 I can understand the more efficient burning on two hence the extra 300 rpm.

 But when run on either the left or right mag the engine is not as smooth as when on two. WHY??

 A car has only one set of plugs and that runs smooth,  So at 4000rpm on two smooth 3710 rpms on one not as smooth ??

 

 Alan

 

 

 

 

 Read this topic online here:

 

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Alan Carter

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

Posted: Wed Jun 19, 2013 3:22 pm Post subject: Re: Daul Mags on the 914

Thank you Barry.

All of that seems to make sense, well it does make sense, i am just surprised the difference in makes, as its about the same roughness on each mag, and as you say much smoother on two.



Regards 

Alan

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ploucandco

Joined: 16 Sep 2007
Posts: 69

Posted: Wed Jun 19, 2013 4:57 pm Post subject: Re: Daul Mags on the 914

Alan, what were your mag drop figures before the HT coil replacement? Also, did you clearly see on the spark plugs (different colors) that you had an issue with an HT coil?



Thanks, Jacques.

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Alan Carter

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

Posted: Thu Jun 20, 2013 12:44 am Post subject: Re: Daul Mags on the 914

Hi Jacques.

My mag drops have always been around the 300 mark.

I had the same problem under a year ago and ended up swapping coils over

left to right to confirm it was a ht coil.

I did not make a note and have forgotten which one it was , so it could be the previous new one, and maybe i should have cleaned the connectors first. but its too late now, Can i get a the mag  coil tested now its off??? 

 

Obvious drop 500 + and rough running and banging ,

Did all the usual , swapped caps, and plugs,

Standard coffee colour , Did note here that the Densol plugs burnt much cleaner the the NGK , WHY ?

The plugs in the UK are about Â£10 each for the 914, and about Â£2 on the net,

so email Densol , are they and different, No universal to the number.

  

Run the engine 1 minute  felt the temperature  front bottom plugs colder, took them out, looked slightly wet, so guessed that was it.



Regards

Alan

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ploucandco

Joined: 16 Sep 2007
Posts: 69

Posted: Tue Jul 02, 2013 2:42 pm Post subject: Re: Daul Mags on the 914

Hello Alan,



Can you tell me how you came to the conclusion that you need to replace an HT coil and which one to replace?



I seems to have the same issue you had in the past, went to a ROTAX dealer who analysed my engine and told me that the issue is with the carbs and not the ignition. But was not able to solve it...



Thanks, Jacques

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