[AT] Kubota M5700 noise

Mon Apr 6 11:31:18 PDT 2020

 Harmonic damper?

-----Original Message-----
From: Ken Knierim <ken.knierim at gmail.com>
To: Antique Tractor Email Discussion Group <at at lists.antique-tractor.com>
Sent: Mon, Apr 6, 2020 11:06 am
Subject: Re: [AT] Kubota M5700 noise

Really reaching a bit here... I had a persistent rattling noise I chased in my Blazer. It made enough racket that the spark retard system would kick the timing back. Tried all kinds of things; kept thinking it was a rod or something. I finally got an engine to upgrade from the 305 to a 383 (stroker 350). When I tore it apart, I found the bolts on the torque converter to the flex plate had slipped and were rattling. Had to replace the flexplate to fix it but the noise sounded in the engine and wasn't. 
Yours sounds like a particular cylinder from the video but is it possible there's something loose in the bell housing?
Ken in AZ
On Mon, Apr 6, 2020 at 10:40 AM Dave Maynard <dave at themaplehillfarm.com> wrote:

Actually, did not check length of connecting rod and its clearance from head at TDC. But it's not traveling to close to the head as there would be damage showing. Just have this new concern about the wrong rod being put in by mistake, but that would have been short, not long.
Dave
On Mon, Apr 6, 2020, 1:01 PM Mike M <meulenms at gmx.com> wrote:

  When you had it apart, did you check all the piston,ring and bearing clearances?

 Mike M

 On 4/6/2020 11:35 AM, Dave Maynard wrote:

 No sleeves in this engine. Someone had this engine apart before and #5 had a new piston and rod and bearings. The seller said it was his father's tractor since new and never been apart....he lied! There was more RTV on oil pan than you could imagine and obviously that piston and rod and bearings had been replaced and I thought they had been chasing the noise. Unless there was some other reason, but dont know.       My friend and mechanic help has a Jacobson mower he's is rebuilding that has a 4 cylinder version of this motor that appears identical except the number of cyl's. He found the rod to be the same except it a tweak shorter by an almost immeasurable amount, maybe .005 or .010. Part number is almost the same except last digit and now I'm wondering if that could be someone's mistake. Would shorter rod cause preignition? By the way, there is no part number on the rods so they would have to be accurately measured.      It's going to be a bit before I can get this back apart again, but hoping to have this fixed in time to plow. 
  Dave  
  On Mon, Apr 6, 2020, 9:08 AM Cecil Bearden <crbearden at copper.net> wrote:

  That was one of my thoughts, but my experience has been that the liner movement was a double "thud" once on down stroke and once on upstroke.  
 Cecil
  On 4/6/2020 1:12 AM, k7jdj at aol.com wrote:

   Cylinder liner loose.  Don't know if this engine even has cylinder liners if it does and that liner is moving you would get click. Did you look carefully at the head when you had it off and look for any sign of head distress? I would do a compression check as well. 
  Gary 
  Renton, WA.

  -----Original Message-----
 From: Roger Moffat <rogerkiwi at gmail.com>
 To: Antique Tractor Email Discussion Group <at at lists.antique-tractor.com>
 Sent: Sun, Apr 5, 2020 7:43 pm
 Subject: Re: [AT] Kubota M5700 noise

  On Apr 5, 2020, at 9:59 PM, Dave Maynard <dave at themaplehillfarm.com> wrote: 
 Have cracked injector lines one at a time, and it gets quieter on #5  

 But only on #5? 
  When you crack the others the engine misses, but the noise remains? 
  I wonder if something about cylinder 5 is somehow different so that the compression is higher, and so it’s igniting (pre-igniting) too much before top dead centre in just that cylinder? 
  Eg #5 piston slightly higher than the other 4? 
  Roger   _______________________________________________
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