[NSRCA-discussion] OS 120 AX

[Bob Richards]

John,
   
  Not much time on the engine, I think the bearings are fine but will see about getting a new rear bearing on order.
   
  I think I finally figured out the bad running today. I put known good fuel in it and still had poor power, even with a 15x8 prop. Frustrated, I pulled the head to see if I could see any problems. The sleeve came out with the head, it was stuck to it. The locator pin in the case that keys with the sleeve was broken off, and the sleeve was rotated about 15 degrees out of position. The ports were not lining up correctly! I could tell by the film on the outside of the sleeve that it had been lined up properly at one time, so the engine has obviously been apart before. After I lined it up, it ran much better. Oh, the sleeve looked good, I could not see any real wear. I'll probably tear down the engine completely just to check everything out better.
   
  I still need to play with the mixture, the needle is VERY broad, and it seems to need to be really rich on the ground to run best in the air. Vertical was awesome. Pushing out of an outside loop seemed to lean out, so I am going to look closer at the tank installation. I am also going to reinstall the muffler baffle to give a little more muffler pressure, which should improve the fuel draw.
   
  I've got a 15x10 prop as well, I may install that and compare my rpms with those reported in an earlier post.
   
  Bob R.
  

John Pavlick <jpavlick at idseng.com> wrote:
          Bob,
   How much time is on it? We've had a few around here that ate the rear bearing in 50 - 100 flights. One of them ended up ruining the sleeve too (bearing debris). The solution is to replace the rear bearing with an OS 140Rx F.I. (sealed) bearing before it gets bad enough to cause other damage. The front bearing is a double sealed type already so you won't need to change that one. This is a really good running motor when you get the bearing thing straightened out.
   
  John Pavlick
http://www.idseng.com
    ----- Original Message ----- 
  From: Bob Richards 
  To: NSRCA Mailing List 
  Sent: Monday, September 03, 2007 8:35 AM
  Subject: [NSRCA-discussion] OS 120 AX
  

  I acquired a plane with an OS 120AX installed, and seem to be having some issues with it. It came with an APC 16x8 prop and stock muffler. Is not running as well as I think it should, but I did figure out I had some bad fuel. I plan to go out again today and tinker with it some more.
   
  What fuel, prop, and what rpm figures should I be seeing?
   
  Thanks in advance.
   
  Bob R.
   
    
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