Interesting Motor Discovery-OS1.60

[Karl G. Mueller]

Bob,

The problem with the ring being tight in the groove occurred as well on some 
of the old O.S. 60FSR's. I think O.S. sometimes works to too close a tolerance.
I like the clean machined finishes and general quality of the O.S. products.
To free up the ring you would have to get a piece of 600 paper on a flat surface
and try to sand the sides of the ring smooth and free of machine marks by applying 
a gentle pressure with three fingers. If the ring is too tight you will get surging at 
the  higher revs. On some strokes the ring will seal and on some strokes it will 
not and it looses the compression.
Just as a matter of interest what type of fuel were you using and also did you find that the O.S. 160 has enough power on a muffler to fly the G.P. 300S ?

Karl G. Mueller
kgamueller at rogers.com


----- Original Message ----- 
  From: Bob Pastorello 
  To: NSRCA 
  Sent: Saturday, April 17, 2004 3:25 PM
  Subject: Interesting Motor Discovery-OS1.60


  Finally got around to getting the Wagstaff Extra airworthy, after not being run for the winter.  Felt rough, so tore it down.  Bearing was not really bad, although a little rust was present (wasn't a SS bearing).  Upon investigation, noting the serious lack of compression, I proceeded to replace the bearing.
      While the piston was out, of course I cleaned it....lo and behold...RING rusted SOLID in the groove.  After careful working with my Amsoil spray, it freed, and I cleaned the groove.
      What was interesting was oil on top of the cylinder, and on the cylinder wall (not a lot, but a film was there)...and the side of the piston around the ring groove was bone dry.

  Fixed it all up, ran like a top, very smooth - so shoudl be good to go.  I have never seen a ring stuck like this before, and just thought I'd share the tale in case anyone runs into inexplicable roughness and low compression....

  Bob Pastorello
  rcaerobob at cox.net
  www.rcaerobats.net

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