YS-91 almost done

[Verne Koester]

Ken,
Yes, lashing the valves is setting the clearance between the rocker arm and the valve stem. Not sure what it's supposed to be on a 91. On the bigger YS engines, it was about .004" and it's set with a feeler gauge. You need to purchase some new bearings and come over to my house. I can show you most of this stuff faster and easier than I can explain it. 

Verne


  ----- Original Message ----- 
  From: Ken Thompson 
  To: discussion at nsrca.org 
  Sent: Wednesday, June 08, 2005 6:50 PM
  Subject: Re: YS-91 almost done


  Verne,

  I've already got it back together and in the plane.  I used a small brush to clean the inside of the head, as best as I could, and washed everything out with some old fuel that I keep for this purpose.  The compression seems good, but the problem I have is I never had a new YS-91 so I don't know what it should feel like.  I wiped a little Klotz synthetic oil in the cylinder, before re-assembly, just to be on the safe side.
  I did scrape the entire valve and wiped everything real good. 
  By lashing the valves, I'm assuming you mean to check the back-lash in the rocker arm.  What should that be?  Is there a tolerance for clearance or should it be "just snug"?  I just assembled the rocker assembly the same way I took it off.

  Ken
    ----- Original Message ----- 
    From: Verne Koester 
    To: discussion at nsrca.org 
    Sent: Wednesday, June 08, 2005 6:19 PM
    Subject: Re: YS-91 almost done


    Ken,
    You should be able to scrape the whole valve including the mushroom area where the seal is made. Just scrape down the stem and continue thru the radius and out to the edge. With a #11, you don't have to worry about scraping too hard. You'll see the shiny metal of the valve once the carbon is off. I use one of those "Gunk" brand carburetor dip tanks to clean the head which includes the valve seats. About twenty minutes in the tank, and you'll be able to brush the carbon off the brass seat with an old toothbrush. For some reason, the dip tank doesn't even faze the carbon on the valves. You can get the Gunk brand dip tank at Murray's. Once you've done that, just wash the parts in water as hot as you can stand and blow dry. I've never had the need to lap the valves with toothpaste or anything else. Just reassemble everything and you should be good to go with lots of compression. Don't forget to lash the valves. 

    Verne
      ----- Original Message ----- 
      From: Ken Thompson 
      To: discussion at nsrca.org 
      Sent: Wednesday, June 08, 2005 5:28 PM
      Subject: YS-91 almost done


      Well folks, 

      This is what I did, I pulled the head and took it apart just like Mike Darr told me to do.  I didn't even lose the spring retainers.  
      I chucked the stem up in my Dremel and cranked it up on high, having some plumbers sandpaper handy I ran a strip of 100 grit on the stem until it shines like new!  That ought to do it!!  

      Not really, I did just like Verne told me too and used a # 11 and scraped it gently just until the rough stuff was gone.  I wiped the stems with a rag and am ready to re-install the valves.  I am going to use toothpaste to re-seat the valves and my question is, when I'm done with that can I just wipe the excess off or do I need to clean it with something special before re-assembly.

      Thanks in advance,
      Ken
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