YS-91 AC problem

[John Ferrell]

I use this method as well.

Don't forget Eric Henderson's tip to do the disassembly/assembly inside a gallon zip-lock plastic bag unless you enjoy hunting for valve keepers.

The carbon build up is a normal condition and should be expected of YS engines that experience long service intervals.

I prefer to adjust YS valves by feel. With the valves all the closed, there should be a perceptible "wink" in the rocker to valve contact.  After reassembly it may be necessary to adjust this several times in the first ten flights or so.

Expect the clearance to get smaller as the valve finds its seat.

Tight valves cost horsepower, loose valves break valve train parts and cost horsepower.

John Ferrell    
http://DixieNC.US

  ----- Original Message ----- 
  From: Ihncheol Park 
  To: discussion at nsrca.org 
  Sent: Thursday, June 02, 2005 10:52 PM
  Subject: RE: YS-91 AC problem


  I took the valve out of the head and chuck it up on dremel (not so hard).  Then, turn it on a dishwashing sponge that has blue scrubbing thing (green ones, the heavy duty is not recommended).  I do it with a little soap on the wet sponge.  After finishing, I remove the valve from the dremel and hold it with rubber sponge.  Then use the scrubbing sponge on the side where it was chucked up on Dremel.  Do it slow and watch the valve carefully to prevent damage.

  Ihncheol Park




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  From: discussion-request at nsrca.org [mailto:discussion-request at nsrca.org] On Behalf Of Robert Harden
  Sent: Thursday, June 02, 2005 9:33 PM
  To: discussion at nsrca.org
  Subject: Re: YS-91 AC problem


  I don't remember Bill saying, but you have to remove the valve stem from the guide first.  Then I used a small piece of fine sandpaper twisted and ran it through the guide up and down until the carbon was removed.  Maybe there is a better way to do this - any one have suggestions?  Now then, so that this doesn't happen again, use a fuel that has all synthetic oil (no caster oil in it).  Hope this helps.

  Bob
    ----- Original Message ----- 
    From: Paul Horan 
    To: discussion at nsrca.org 
    Sent: Thursday, June 02, 2005 8:29 PM
    Subject: Re: YS-91 AC problem


    Ken,
        What did he tell you to do the cure the carbon problem.
    Thanks,
    Paul
      ----- Original Message ----- 
      From: Ken Thompson 
      To: discussion at nsrca.org 
      Sent: Thursday, June 02, 2005 7:22 PM
      Subject: YS-91 AC problem


      Thank you to all who gave me places to look for my problem.
      Somebody gave me the thought that maybe it was carbon deposits on a valve, I'm sorry I don't remember who.  I dismissed this theory because the valves seemed to be operating properly.
      Early this morning Mike Darr stopped by to check out my damaged Excelleron and took a look at my motor for me.  He manually worked the valves and all of a sudden the compression came back.  It looks like there was carbon on the valves after all.  He told me what to do and I should have it fixed as soon as I get back from Norfolk, a little trip this weekend to go out for the day on the USS Theodore Roosevelt.
      Thank you all again and thanks to Mike for showing me what to do.

      Ken Thompson
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