[AT] Kubota M5700 noise

Dave Maynard dave at themaplehillfarm.com
Mon Apr 6 08:35:14 PDT 2020


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> <rogerkiwi at gmail.com>
> To: Antique Tractor Email Discussion Group <at at lists.antique-tractor.com>
> <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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