[AT] Kubota M5700 noise

Cecil Bearden crbearden at copper.net
Wed Apr 8 12:01:49 PDT 2020


Usually a piston pin bushing will produce a double knock. 
Usually..............  Just like an old farmer once told me when in the 
middle of a drought.   I said:"The cows are grazing in the heat of the 
day.  That's a sign of rain" He said: "All signs fail in dry weather"
Cecil

On 4/8/2020 11:57 AM, Dave Maynard wrote:
> 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 
> <mailto: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 <mailto: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 <mailto: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 <mailto: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 <mailto: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 <mailto: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
>>                     <mailto: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 <mailto: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
>>>                             <mailto: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
>>>                                 <mailto: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>
>>>>                                 <mailto:rogerkiwi at gmail.com>
>>>>                                 To: Antique Tractor Email
>>>>                                 Discussion Group
>>>>                                 <at at lists.antique-tractor.com>
>>>>                                 <mailto: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
>>>>>                                 <mailto: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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