[f-AA] Short spark plug

[Kyle]

We used to do this on Kawasaki 600 Ninja's, in the early 90's. They were notorious for carboning up the valves, and losing compression. The theory is, the sprayed water hits the red hot carbon, and shatters it off the valve. I dunno, it worked on those engines, for awhile. Then again, they didn't fly. Water injection works, on a lot of vehicles, but I would worry about unknown damage to the valves, on something I could not pull over and call AAA. That's my less than .02c worth. Regards, Kyle
  ----- Original Message ----- 
  From: Ken Lessard 
  To: aeronca at westmont.edu 
  Sent: Wednesday, November 01, 2006 4:28 PM
  Subject: Re: [f-AA] Short spark plug


  Hello Bill in NH,
    In regards to your compression loss I would like to offer a past experience I had and maybe it can benefit you . There a several possibilities for the loss of compression, the worst being a cracked exhaust valve or burnt valve seat so I will share mine with you and this group. This is a cut and paste from a topic I responded to on the Aeronca L3 site recently. I only post it here for your consideration and not, by far, a recommendation. It's just something that worked for me a long time ago... I also came up with a way to ream the exhaust valve guide on my friends C-172 with an 0300, that had a history of sticking exhaust valves, without pulling the jug...That's another story in itself...   Ken in MA

   "Hi John,
  I was just wondering if you determined where your compression loss
  was coming from during the leak down test. Years ago I had the same
  problem with my C-75 engine in my Ercoupe. My #1 cylinder was 55/80
  and my IA friend suggested that I make a determination where the
  loss was before ripping into the engine. With the cylinder
  pressurized with air I took off the oil cap and listened, no sound
  so the piston and rings are good. Next I put my ear to the carb.
  intake, no sound so the intake valve was good. Lastly I put my ear
  to the exhaust and heard lots of air rushing. Hmmm, seems to be a
  bad exhaust valve. Way back then, the only fuel option was 100ll. 80
  octane was gone and mogas was not legal yet so we had major problems
  with lead deposits in the cooler running cylinders. Now, hang on
  because I'm gonna tell ya what I did to fix it (under direction from
  the IA). I pulled the air filter and cowl and ran the engine up to
  temp. We brought the engine up to 1800 RPM and sprayed atomized
  water into the carb. inlet using a pump type garden sprayer. Very
  little at first and increased the volume of water until the engine
  started to loose RPM. I was stunned to see all the black crap that
  belched out of the exhaust. I did this two times and the second time
  the exhaust was clear. The next compression test #1 was up to 77/80
  and all the cylinders came up to 76/80 to 78/80. I'm not
  recommending this procedure but it sure worked for me. The
  compression stayed up through the next 4 annuals until I sold the
  plane.. Just a thought... Ken"
   
    ----- Original Message ----- 
    From: Bill 
    To: aeronca at westmont.edu 
    Sent: Wednesday, November 01, 2006 5:54 PM
    Subject: [f-AA] Short spark plug


    Hi.We are doing our annual on Moya (1946 7AC) and the IA I'm working with said I should put the Short plug in the front cylinder.Can someone tell me the numbers for it and a good supplier for an A65.I've got one cylinder reading low (45/80) and we can hear the air coming out the exhaust.The others all read 71/80 and have about 500 hours on them.He seems to think the valve is sticking becouse I run mostly pump gas and don't use(sorry to start any wars ) MMO.We're going to run the motor to warm it up and check again.Has anyone else ran into this problem before. Thanks. Bill in N.H. 2505E
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