[AT] Kubota M5700 noise
Cecil Bearden
crbearden at copper.net
Wed Apr 8 07:36:22 PDT 2020
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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