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JD 425 sputters, quits, backfires ?


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#1 Alberta Bolens ONLINE  

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Posted September 10, 2015 - 06:32 PM

Good day.

My JD 425 with 1900 hours started acting up this summer.  It will quit or start to sputter and miss. If it quits it is hard to start sometime not firing or it will backfire.  By the way these things will run backwards.  Which can't be good for it.  It is happening more often now.

 

I put steel cam in it around 1200 hr so it shouldn't be timing issue.  

 

I haven't checked the plugs, where replaced with cam.  As the problem comes and goes I don't think its the plugs.  I think its an electrical component that is getting week.

 

Any thoughts on this?


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#2 chieffan ONLINE  

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Posted September 10, 2015 - 06:58 PM

Better check the key in the flywheel.  It could be partially sheared and changing the timing.  Flywheel could also be loose enough to be moving slightly with the partially sheared key.  Don't take much to throw things out of time.


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#3 EricFromPa ONLINE  

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Posted September 10, 2015 - 07:07 PM

1900 hours is quite a few hours for an aluminum block engine.

 

 

 

My Cub with 16hp briggs twin had almost that many hours on it and it started chugging backwards when you shut it off on a warm day.I knew the rings were getting worn because it was down on power from what it used to be.(or so I thought) I checked the valves and reset them and it helped a bit.I pulled all the tins off the engine and gave it a good degreesing while I was at it.I also pulled the flywheel and was surprised when i found the flywheel key was worn.It wasn't sheared but it sure was offset a bit.

 

After replacing the flywheel key and a good cleaning and fresh valve adjustment and new valve cover gaskets it ran like a new engine again.Well as new as it could run with 1,696 hours on it.

 

A few months later the pump went out in the tranny and it became a parts doner.  :wallbanging:  :rolling:


Edited by EricFromPa, September 10, 2015 - 07:09 PM.

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#4 propane1 ONLINE  

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Posted September 10, 2015 - 07:16 PM

Sounds like timing trouble. Also check to see if it is running with a lean gas mixture. That would cause it to run hot, that can do funny things to an engine. Noel
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#5 Auburn David OFFLINE  

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Posted September 10, 2015 - 07:16 PM

Flywheel key..



#6 Username OFFLINE  

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Posted September 10, 2015 - 07:49 PM

A 425 has 2 pulser coils and one or both could be defective.


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#7 Auburn David OFFLINE  

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Posted September 10, 2015 - 08:17 PM

A 425 has 2 pulser coils and one or both could be defective.

But check the key first ..no?



#8 Username OFFLINE  

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Posted September 10, 2015 - 08:42 PM

But check the key first ..no?

I would think if it were the key it would not run good sometimes and then start acting up if in fact  it does run good sometimes.I am leaning towards an electrical issue.


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#9 Alberta Bolens ONLINE  

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Posted September 10, 2015 - 08:53 PM

So I checked the plugs.  One was black fowled up and the gap was wide.  the other one was clear and the gap was close to being set.  I cleaned them both up set the gaps.  It still started rough but then seemed to run fine.  Went pushed dirt for 1/2 hour seems to run fine.  New plugs tomorrow.

 

When I did the cam, the fly wheel key was tight no signs of wear that was only 600 hours ago.  I'm not really suspecting it.  If it keeps acting up I will test the pulsar coils.

 

The temp gauge sits mid way when I'm working it.  T

 

This problem comes and goes, hot engine, cold engine.  Sometime run great for hour, next time it will only run 5 minutes before acting up.


Edited by Alberta Bolens, September 10, 2015 - 08:56 PM.

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#10 Auburn David OFFLINE  

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Posted September 10, 2015 - 08:55 PM

I would think if it were the key it would not run good sometimes and then start acting up if in fact  it does run good sometimes.I am leaning towards an electrical issue.

what he describe has been a key in my case 2 times with a Kohler 20..but I dont know anything about the older ones.



#11 Auburn David OFFLINE  

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Posted September 10, 2015 - 08:57 PM

So I checked the plugs.  One was black fowled up and the gap was wide.  the other one was clear and the gap was close to being set.  I cleaned them both up set the gaps.  It still started rough but then seemed to run fine.  Went pushed dirt for 1/2 hour seems to run fine.  New plugs tomorrow.

 

When I did the cam, the fly wheel key was tight no signs of wear that was only 600 hours ago.  I'm not really suspecting it.  If it keeps acting up I will test the pulsar coils.

 

The temp gauge sits mid way when I'm working it.  T

 

This problem comes and goes, hot engine, cold engine.  Sometime run great for hour, next time it will only run 5 minutes before acting up.

WOW..that would be luck!!!(well not mine)



#12 Alberta Bolens ONLINE  

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Posted September 10, 2015 - 09:11 PM

WOW..that would be luck!!!(well not mine)

I'm not holding my breath.  



#13 JDBrian OFFLINE  

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Posted September 11, 2015 - 06:54 AM

Could be an electrical issue. I'd give the wiring harness a good going over looking for bad connections, burnt or discoloured connectors, chafed wires etc. Since the plugs have 600 hrs on them it's a good idea to replace them first. If you are still getting a fouled plug on one side with a new, properly gapped plug I would go looking for a spark problem on that side. You may be able to get a service manual for that engine from the Kawi site. JD doesn't allow free use of it's manuals. 



#14 chieffan ONLINE  

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Posted September 11, 2015 - 07:09 AM

I have found that NGK plugs will last a lot longer than Champion.  I am not a fan of Champion spark plugs.  Way to many problems with them.


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#15 Alberta Bolens ONLINE  

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Posted September 11, 2015 - 06:58 PM

I have service manual CD for 425,445,455.  Its useful.  I did put in new plugs tonight .  I need to work it for while se how it goes.  


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