[NSRCA-discussion] OS140rx problems - help needed.

[John Pavlick]

Colin,
 When you replaced the bearing did you notice how the ring was installed on
the piston? I know this causes problems on the OS160 - there is a very small
alignment pin in the piston ring groove that locates the end of the ring.
The ring needs to be indexed so that it aligns properly with the ports. It's
possible to put the engine back together with the ring misaligned if you're
not careful and this would distort the ring badly enough to make the engine
run poorly. Believe me, I've seen guys do it. I would carefully disassemble
the engine again, noting the position of the ring. At this point it probably
wouldn't hurt to just replace the ring + sleeve anyway. I don't know how
long they last on a 140 - maybe someone else can answer that. I had the same
sort of problem with an old 46 SF - very similar symptoms to what you're
describing. Turned out to be a ring + sleeve. Engine is as good as new now.

John Pavlick
http://www.idseng.com


  -----Original Message-----
  From: nsrca-discussion-bounces at lists.nsrca.org
[mailto:nsrca-discussion-bounces at lists.nsrca.org]On Behalf Of colin
chariandy
  Sent: Saturday, April 29, 2006 12:13 AM
  To: NSRCA Mailing List
  Subject: [NSRCA-discussion] OS140rx problems - help needed.


  Hello

  I started having problems with my 200-300flight old rx last season after I
lost my muffler ( Bolly 460) in flight. I decided to upgrade from a muffler
to an Aeroslave pipe. The motor ran poorly on the pipe and I blamed the
set-up. Poor midrange required that I back out the pump 3/4 and set the top
end a bit lean for reliable operation in the air. The setting would change
from one flight to the next. On the ground the engine would load up and
eventually quit 1/2 the time. I have now gone back to a muffler ( Bolly 590)
and the engines runs exactly the same as on the pipe...very poor mid-range,
erratic operation.

  Previous bearing replacement was the stock item put in 50 flights before
the problems started.

  I'm going to guess I need to replace the main bearing. What should I buy
and where? What else should I check/replace ? When should ring/sleeve be
replaced? Does anything else go wrong with these engines...pump problems ?

  All inputs are welcome.
  Colin.




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