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Well, if this sounds familiar you are correct.  I was working with Bill Hertzel, who was very helpful in guiding me through a logical and detailed diagnostic routine and we were sure that the problem was solved.  I've been waiting for nicer weather to enjoy the fruits of my labors.  Well, I still have a problem.  I noticed a miss and again shortly after start up, but it seemed to go away.  I did a 1 hour flight and decided to pull the plugs and take a look.  What I found was that on cyl #3 both top and bottom spark plugs were extremely clean, while the others were quite sooty.  If Bill would consider offering his help again on this, I would be extremely grateful.  I have done a bit more investigating and can hopefully offer some thoughts, but I really need help, and I have pictures  Thanks.....Tom

Bill, if you would like to chat with email or cell, feel free.  Email:  tomscub At gmail Dot com or
618 - five four one - Zerro 775

 

  • Re: Misfire Module B

    by » 4 months ago


    Lets see if I can add a pic link here

    25703_2_IMG_0329 2.JPG (You do not have access to download this file.)

  • Re: Misfire Module B

    by » 4 months ago


     Well, it looks like something common to both plugs in the same cylinder which tends to rule out the electrical side of the equation.

    I am guessing you have replaced the plugs because the threads should be very White from the coating of Heat Sink compound that does NOT appear to be on them. ???

    What sounds like a miss might actually be Early Ignition/Detonation from a Hot Plug that is blowing the soot off the plug.

    Is there Heat Sink Grease on the threads that just doesn't show in the photo?

     


    Bill Hertzel
    Rotax 912is
    North Ridgeville, OH, USA
    Bill.Hertzel@Yahoo.com
    Clicking the "Thank You" is Always Appreciated.


  • Re: Misfire Module B

    by » 4 months ago


    Yes, there is heat sink paste on the threads.  Thank you for sticking with me on this.  I did a couple pf things. I pulled the right intake manifold and checked the o ring seals.  Both were good.  I also checked the alignment of the carb piston just to make sure that it was aligned by the diaphragm tab was doing its job.  Not sure where to go next.........Tom 


  • Re: Misfire Module B

    by » 4 months ago


    It just doesn't make sense to me.  You are right, electrical is virtually ruled out, but how can cyl #1 look sooty (plenty of fuel), and #3 be dry and running lean?  After the start and warm up I tried to do the ignition test.  I had a difficult time getting the rpms up to 4K.  At about 3400 is got so rough and I had to add significant throttle to get it to move. It was actually falling on its face. Finally when I did get the rpm up, the ignition check was pretty good, so I took off and flew it thinking that I had a fouled plug from the long warm up. But I decided to pull the plugs and to take a look, just to verify....Tom  


  • Re: Misfire Module B

    by » 4 months ago


    Just throwing out ideas to see which ones might stick.

    Let's consider a leaking intake manifold at the #3 cylinder.

    It leaks air until things heat up, expand, and seal.

    There might be a hidden fracture somewhere.

    Spray some brake cleaner on the area when it is running rough.

    Any change, Better or Worse, indicates the fluid is making it to the cylinder.

     


    Bill Hertzel
    Rotax 912is
    North Ridgeville, OH, USA
    Bill.Hertzel@Yahoo.com
    Clicking the "Thank You" is Always Appreciated.


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