Engine problem John deere 40

Mikemul

Member
i have a problem with my john deere 40, when the tractor idles there is no problem. only when you accelerate it starts to pop softly. it runs at a fixed speed but through that you hear a popping sound every now and then. who knows what this can be? I have already put new bows and bows caps on it.
 
OK, I'll bite. I have had 40s and 420s for over 45 years and I have no idea what "bows and bow caps" are.
Peter
 
My 40 has a bit of a pop to it. That is why they are called Johnny Poppers. My MT before that did as well.

Now if it is backfiring with a bang like a gun going off that is different and something that can/should be addressed. Have you ever checked the timing? If it is backfiring I would start with making sure it is timed correctly. The best way to do this is to obtain the owners manual and follow the instructions outlined in there but use a timing light. All you need is a cheap timing light which you can find on ebay or amazon. If your 40 is 6 volt you will need a 12 volt battery to run the timing light. I have used the battery in my truck or other 12 volt tractors to do this.
 
it is a two cylinder odd fire engine sharing one intake port and a one barrel carb. All such engines tend to have a miss on one cylinder at idle .
Assuming the compression and valve lash are in spec ?
A leaking intake manifold gasket, eroded head gasket surface, eroded manifold gasket surface or a cracked/rusted manifold can also cause the stuttering and puttering.
 
Might be as simple as needing the load mixture screw opened up a bit. It is the one on the bottom of the carb.
 
(reply to post at 16:30:10 06/22/20)

I have set the ignition to the spark on the flywheel that the contactpoints begin opening. The flywheel Turns to fast for the light to see. I have set also the valves. I think its a problem with the carburator. Check the video here. https://m.youtube.com/user/schaap418
 

Autolite non resistor 437 sparkplugs work well in those engines. Ignition wires should be solid core .
Is the popping more pronounced when the engine is cold or hot ?
 
(quoted from post at 21:44:01 06/22/20)
Autolite non resistor 437 sparkplugs work well in those engines. Ignition wires should be solid core .
Is the popping more pronounced when the engine is cold or hot ?

Thanks for youre comment, I wil look if there is a good contact in the wires. There is no difference between hot or cool engine. Only a problem with mre rpm stationair is great. What about the points?
 
(quoted from post at 16:10:49 06/22/20)
(quoted from post at 21:44:01 06/22/20)
Autolite non resistor 437 sparkplugs work well in those engines. Ignition wires should be solid core .
Is the popping more pronounced when the engine is cold or hot ?

Thanks for youre comment, I wil look if there is a good contact in the wires. There is no difference between hot or cool engine. Only a problem with mre rpm stationair is great. What about the points?

Occasionally the lobes on the distributer shaft will lift the points open farther for one cylinder than the other.
 
(quoted from post at 22:56:54 06/22/20)
(quoted from post at 16:10:49 06/22/20)
(quoted from post at 21:44:01 06/22/20)
Autolite non resistor 437 sparkplugs work well in those engines. Ignition wires should be solid core .
Is the popping more pronounced when the engine is cold or hot ?

Occasionally the lobes on the distributer shaft will lift the points open farther for one cylinder than the other.

That can be true. But how can we fix that. When I check the sparkplugs after running and they look black and not wet
 
I listened to the video. I don't believe
that is a fuel problem. Weak points
spring allowing bounce, timing, valve
lash too tight, or bad manifold in that
order.

A timing light only flashes when the
number one cylinder fires. You can see
the mark on the flywheel at any speed. I
will post the page from the manual later
when I can get to my computer.
 
Sorry I missed that you already set the valves. Also forgot to mention carbon tracks or a crack in the distributer cap.
 
(quoted from post at 12:22:06 06/23/20) Sorry I missed that you already set the valves. Also forgot to mention carbon tracks or a crack in the distributer cap.

You mean carbon tracks on the sparkplug and plugcap? There a no cracks in the distrubitor cab
 
No, the carbon tracks would be inside
the distributor cap. Just a dark line
that looks like you marked it with a
pencil.
 
Links won't work. Here's the manual pages for an M. 40 & 420 is the same.


cvphoto48292.jpg


cvphoto48293.jpg
 
(quoted from post at 03:06:22 06/24/20) Links won't work. Here's the manual pages for an M. 40 & 420 is the same.


<img src="https://www.yesterdaystractors.com/cvphotos/cvphoto48292.jpg">

<img src="https://www.yesterdaystractors.com/cvphotos/cvphoto48293.jpg">

18888-E80-C103-490-E-AAE7-8-B3-C3-ABE582-E.jpg


F7-BE607-B-0-C94-4-E46-90-F7-74-FF7854-E1-A2.jpg


Here the working pictures
 
From the second picture I can tell the
timing is off IF the oil pump is timed
correctly. It would be best to use a
timing light at full throttle per the
instructions from the manual.

With no timing light you have to put the
rotor on and turn it to the advanced
position and hold it there while you
also turn the distributor to where the
points have just opened and tighten it
down. The point gap must be set
correctly first!
 
I doesn’t understand the text while you doesn’t have a timing light. Put the rotor on where? And what do you mean with advanced position? You mean I set the contact point to the good value and than turn the engine to the spark mark. And than set the ignition to begin opening points ?
 

Are you using a high intensity timing light that flashes to illuminate the timing mork on the flywheel as the engine is running ?
Or just using a 6V test lamp across the points and are rolling the engine by hand ?
 
Yes - set the contact point to the good value and then turn the engine to the spark mark.

Next put the rotor on top of the distributor shaft where it normally goes. Turn the rotor by hand as far as it will go. It will only turn one way. This is the advanced position. When you let go the advance springs will pull it back to where you started.

Hold the rotor in the advanced position and then set the ignition to begin opening points.
 
Hi, i have set the ignition with the timing light at full rpm. now its much better at high rpm and no pops more. here is a video. is this how it post to be?

link: https://www.youtube.com/watch?v=X56s1bFY41M

Greetings Mike Mul
 

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