ST2300 conrod, wrist pin end

[Ed Miller]

In looking at this failure it appeared at first the bottom half of the conrod wrist pin bushing was worn, thus an egg shaped hole. At least that would make sense to me. However that isn't the case, the bushing ID is round, so the wear seems to be to the entire bushing. I'm beginning to believe the bushing to wrist pin fit was a tad loose from the factory or the finish on the bushing bore was poorly done and from normal running the bushing wore out to the point it affected performance in a big way. If the wrist pin finish was "aggressive" the piston bores would be worn which is not the case. In any event, once I receive the new conrod I'll improve the oiling for the wrist pin. 
Hmmm, 2- ST2300's are approximately $400, 'bout the same as one OS 140 or Webra 145. Still a good value for an 11lb airplane. 
No Ron, the OS and ST rods are different <G> but it appears the rear bearings on both engines are the same. I happen to have a couple of SS rear bearings in stock for my RX....
Ed M.
  From: ronlock 
  To: discussion at nsrca.org 
  Sent: Tuesday, June 24, 2003 6:48 PM
  Subject: Re: ST2300 conrod, wrist pin end


  Ed,  Maybe an OS 140RX rod would fit, they are "only"  $34.99.  <G>
  Ron Lockhart
    ----- Original Message ----- 
    From: Ed Miller 
    To: discussion at nsrca.org 
    Sent: Monday, June 23, 2003 11:37 PM
    Subject: Re: ST2300 conrod, wrist pin end


    Oh sure, Tower will gladly sell me a new conrod for the bargain price of $39.99. That's even a bigger theft than YS parts : )
    Ed M.
      ----- Original Message ----- 
      From: Emory Schroeter 
      To: edbon85 at optonline.net 
      Sent: Monday, June 23, 2003 10:56 PM
      Subject: Re: ST2300 conrod, wrist pin end


      Nope. I haven't had that problem. Can you get a replacement part?

      Emory Schroeter
        ----- Original Message ----- 
        From: Ed Miller 
        To: discussion at nsrca.org 
        Sent: Monday, June 23, 2003 10:41 PM
        Subject: ST2300 conrod, wrist pin end


        Any of you folks out there that have been running ST2300's ever experience a short lived wrist pin end of the con rod ?? I have approximately 100 flights on a ST2300 in a Hanson Dalotel spinning an APC 18x8 with S&W fuels 20% to 30% nitro ( 20% oil in all fuels ) and the bushing in the wrist pin end of the con rod is worn out. I'd say there is at least .030" clearance, maybe more. Engine was down about 700rpm on the ground and never really settled on a rpm and acted lean in the air, in verticals it went flat, would no longer haul plane vertically indefinately. This all happened in maybe 5 or 6 flights, went from a powerhouse to a dog. There is only one small hole in the top of the conrod to lube the wrist pin ( approx .040" in dia. ), the wrist pin is fine and measures no wear at all where the conrod rides on it. I'm going to order a new conrod, if the new one only has one hole in it I may enlarge it a bit as well as add a second hole from the bottom of the wrist pin boss on the rod. Luckily I have a 2nd ST2300, just installed it and I'm back to 8800 rpm on 25% nitro with the 18x8 so I'm ready for the Pocono pattern contest. Both my ST2300's are Italian made, the only notable difference is one has a longer crankshaft ( prop end ).
        Thanks...Ed M.
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