[AT] Kubota M5700 noise

Wed Apr 8 09:46:52 PDT 2020

The tractor in NY you are referring to IS this tractor. That is a post my
son Mike made back when we first got it. You may recognize him on here as
Mangus.

Dave M

On Wed, Apr 8, 2020, 11:58 AM ustonThomas Mehrkam <tmehrkam at sbcglobal.net>
wrote:

> A Google search for  kubota M5700 engine noise  turns up a thread on
> tractorbytenet about a tractor in new york with exactly the same problem.
> Knock piston 5.  You might follow this thread to see if there was a
> solution
>
> M5700 'Knock' and other questions
> <https://www.tractorbynet.com/forums/kubota-owning-operating/413832-m5700-knock-other-questions.html>
>
> M5700 'Knock' and other questions
>
> My father picked up a M5700 this weekend. Overall its in nice shape, but
> we have a couple things we are trying t...
>
> <https://www.tractorbynet.com/forums/kubota-owning-operating/413832-m5700-knock-other-questions.html>
>
>
>
> On Wednesday, April 8, 2020, 9:36:42 AM CDT, Cecil Bearden <
> crbearden at copper.net> wrote:
>
>
> I think the possibility of leftover fuel on the piston might be the
> problem.  Steve O may have figured it out.  It has been many years since I
> did a compression analysis.  Old Dog forgets older tricks thing!!!
> Maybe you can get an application list for the rod number??
> Cecil
> On 4/8/2020 9:11 AM, Dave Maynard wrote:
>
> By reducing compression, would ignition take place at the proper time?
> Would combustion be complete, or would there be leftover fuel that could
> change things on next compression stroke, and maybe pre ignite causing the
> knock?
>
> Dave
>
> On Wed, Apr 8, 2020, 5:18 AM Stephen Offiler <soffiler at gmail.com> wrote:
>
> I just worked out some math.  That engine is 87mm bore x 92mm stroke.
> 23:1 compression.  Swept volume is .547 liter, giving combustion chamber
> volume of .0238 liter.  Now, what-if the con rod was 1mm too short?  That
> adds .0059 liter to the combustion chamber, now .0297 liter, which drops
> compression down to 18.4:1
>
> SO
>
>
> On Tue, Apr 7, 2020 at 7:02 PM Doug Tallman <dtallman at accnorwalk.com>
> wrote:
>
> The rod being too short can't change injector timing or cause
> pre-ignition. It would just mean less compression because the piston
> wouldn't come up as far.  Doug T
> On 4/6/2020 6:24 PM, Dave Maynard wrote:
>
> I know the piston is correct as we replaced it. But James makes a good
> point to ponder, if the rod is too short, it may change injector timing.
>
> Dave
>
> On Mon, Apr 6, 2020, 6:03 PM Bo Hinch <bohinch at gmail.com> wrote:
>
> Or the wrong Piston ( too short or tall ) .
>
> On Mon, Apr 6, 2020 at 12:40 PM 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> <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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