[AT] Kubota M5700 noise

[Dave Maynard]

By the way, not even sure if this has the wrong rod, just been guessing
until we can get it in and apart. I wonder though if there could be
residual fuel from an unfinished burn caused by yet unknown reason. Maybe
carbon buildup in pre combustion chamber which may cause higher compression
or poor atomization. Maybe Cecil's thought of loose or cracked pre
combustion chamber. Unseen crack in the head, causing an improper mixture,
or maybe even a piston pin bearing we missed. Still dont know how soon we
can get it inside and apart, as we need to get a place ready. Don't want it
apart outside, and this time it could be apart a little longer than the
others.

Dave M.

On Wed, Apr 8, 2020, 12:46 PM Dave Maynard <dave at themaplehillfarm.com>
wrote:

> 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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