1952 John Deere A stumbles under load

[LamarsA]

My '52 A (serial number 701144) is a recent rebuild that I had someone do for me and it has less than 10 hours on it. While mowing it began "stumbling" under load and I have not been able to figure out the cause and cure. By "stumbling" I mean that it misses and then I beleive quickly drops a cylinder and looses power. It does not appear to smoke. The plugs are new but are fouled with soot which I recall means it is running rich.
I have tried resetting both the idle and load needles.
I have cleaned the spark plugs.
I took the carb off, tore it down and made sure it was clean, including the various cavities/passages (it was rebuilt along with the engine).
Fuel flow to the carb seems to be fine as far as I am qualified to tell.
My Dad specifically ordered this tractor brand new even though the 60's were coming out. I spent a significant part of my life on it, although less and less as the years passed and I moved away. Dad was always the primary mechanic and I apparently didn't learn quite enough from him before he passed away. Any thoughts and suggestions are appreciated!

 

[ET]

Have you tried hotter plugs?

 

[greenmech]

My '52 A (serial number 701144) is a recent rebuild that I had someone do for me and it has less than 10 hours on it. While mowing it began "stumbling" under load and I have not been able to figure out the cause and cure. By "stumbling" I mean that it misses and then I beleive quickly drops a cylinder and looses power. It does not appear to smoke. The plugs are new but are fouled with soot which I recall means it is running rich.
I have tried resetting both the idle and load needles.
I have cleaned the spark plugs.
I took the carb off, tore it down and made sure it was clean, including the various cavities/passages (it was rebuilt along with the engine).
Fuel flow to the carb seems to be fine as far as I am qualified to tell.
My Dad specifically ordered this tractor brand new even though the 60's were coming out. I spent a significant part of my life on it, although less and less as the years passed and I moved away. Dad was always the primary mechanic and I apparently didn't learn quite enough from him before he passed away. Any thoughts and suggestions are appreciated!

Did you take all the brass plug out and run a drill through the passages? Check for good spark, condenser points. Ron MN

 

[Fixingfarmer]

Most likely electrical. after some consideration the things suggested above are very good I might investigate the coil a little quicker than otherwise as both plugs seem to foul equally if I understand that right? It also is late enough to not have a magneto

Use Autolite 368 plugs. They will still foul every couple years. I’m also taking this as it fouls quicker than that.

Did they put a 12 volt coil on at rebuild or ??? Check the ohm reading from + to - to find out.

Fresh carb gaskets are necessary often each time the carb is removed they peel apart I just got done fighting that issue on a customers carb I go through enough I was contemplating this morning setting up the laser to try to cut some.

Using the loooong correct drill bits on the carb passages

 

[Pappy]

Check the float level. Then emove the float and see if it actually floats.

 

[55 50 Ron]

I worked on a B that had a float that wouldn't float.

 

[Loosehandle]

My '52 A (serial number 701144) is a recent rebuild that I had someone do for me and it has less than 10 hours on it. While mowing it began "stumbling" under load and I have not been able to figure out the cause and cure. By "stumbling" I mean that it misses and then I beleive quickly drops a cylinder and looses power. It does not appear to smoke. The plugs are new but are fouled with soot which I recall means it is running rich.
I have tried resetting both the idle and load needles.
I have cleaned the spark plugs.
I took the carb off, tore it down and made sure it was clean, including the various cavities/passages (it was rebuilt along with the engine).
Fuel flow to the carb seems to be fine as far as I am qualified to tell.
My Dad specifically ordered this tractor brand new even though the 60's were coming out. I spent a significant part of my life on it, although less and less as the years passed and I moved away. Dad was always the primary mechanic and I apparently didn't learn quite enough from him before he passed away. Any thoughts and suggestions are appreciated!

I would guess ignition, weak spark if it has a distributor points gap might be too small.

 

[Fixingfarmer]

Check the float level. Then emove the float and see if it actually floats.

Yes this is another very good thing to check often they crack around the top. If you take it out and put the float in water and see bubbles is a good way to test

 

[sds46a]

My '52 A (serial number 701144) is a recent rebuild that I had someone do for me and it has less than 10 hours on it. While mowing it began "stumbling" under load and I have not been able to figure out the cause and cure. By "stumbling" I mean that it misses and then I beleive quickly drops a cylinder and looses power. It does not appear to smoke. The plugs are new but are fouled with soot which I recall means it is running rich.
I have tried resetting both the idle and load needles.
I have cleaned the spark plugs.
I took the carb off, tore it down and made sure it was clean, including the various cavities/passages (it was rebuilt along with the engine).
Fuel flow to the carb seems to be fine as far as I am qualified to tell.
My Dad specifically ordered this tractor brand new even though the 60's were coming out. I spent a significant part of my life on it, although less and less as the years passed and I moved away. Dad was always the primary mechanic and I apparently didn't learn quite enough from him before he passed away. Any thoughts and suggestions are appreciated!

My 52 A would do the "stumble" and foul the plugs. Found out that even with the choke rod all the way in, the butterfly
remained half way closed causing it to run too rich.

 

[rustred]

Maybe you gave it too much home brew !

 

[Mike(NEOhio)]

I'd agree with sds46a. pull the little cap off the choke shaft. It should be set so the spring pulls the choke shut and the pin pushes it to straight in the bores. Easy to correct if that's the problem.

 

[HFP]

Does it have a mag or a distributor? With either, but the distributors especially, if the condenser is going out they will seem to run fine under no load but once they get loaded up really start to break up. Also with a distributor, a bad coil when cool can work ok then start having fits when it gets hot.

 

[LamarsA]

Have you tried hotter plugs?

Autolite 368 Plugs were suggested. What would be the recommended gap for those?

 

[LamarsA]

Did you take all the brass plug out and run a drill through the passages? Check for good spark, condenser points. Ron MN

I did clean all of the passages. I also now suspect spark although I think it has a new distributer. I will educate myself on Points.

 

[LamarsA]

Most likely electrical. after some consideration the things suggested above are very good I might investigate the coil a little quicker than otherwise as both plugs seem to foul equally if I understand that right? It also is late enough to not have a magneto

Use Autolite 368 plugs. They will still foul every couple years. I’m also taking this as it fouls quicker than that.

Did they put a 12 volt coil on at rebuild or ??? Check the ohm reading from + to - to find out.

Fresh carb gaskets are necessary often each time the carb is removed they peel apart I just got done fighting that issue on a customers carb I go through enough I was contemplating this morning setting up the laser to try to cut some.

Using the loooong correct drill bits on the carb passages

I'd agree with sds46a. pull the little cap off the choke shaft. It should be set so the spring pulls the choke shut and the pin pushes it to straight in the bores. Easy to correct if that's the problem.

Interesting. I will double check. Thank you.

 

[55 50 Ron]

Autolite 368 Plugs were suggested. What would be the recommended gap for those?

.025 is usually suggested. I used .030 on Autolites I recently placed in a tractor.

 

[LamarsA]

My '52 A (serial number 701144) is a recent rebuild that I had someone do for me and it has less than 10 hours on it. While mowing it began "stumbling" under load and I have not been able to figure out the cause and cure. By "stumbling" I mean that it misses and then I beleive quickly drops a cylinder and looses power. It does not appear to smoke. The plugs are new but are fouled with soot which I recall means it is running rich.
I have tried resetting both the idle and load needles.
I have cleaned the spark plugs.
I took the carb off, tore it down and made sure it was clean, including the various cavities/passages (it was rebuilt along with the engine).
Fuel flow to the carb seems to be fine as far as I am qualified to tell.
My Dad specifically ordered this tractor brand new even though the 60's were coming out. I spent a significant part of my life on it, although less and less as the years passed and I moved away. Dad was always the primary mechanic and I apparently didn't learn quite enough from him before he passed away. Any thoughts and suggestions are appreciated!

Thank you all for your advice! It now has hotter Autolite plugs and clean points and it is running as it should!!!! Back to work it goes!

 

[Rich'sToys]

Use Autolite 368 plugs. They will still foul every couple years.

Is that 368 or 386? I only ask because I know they make a 388 and was just wondering if the numbers were similar.

 

[Fixingfarmer]

Is that 368 or 386? I only ask because I know they make a 388 and was just wondering if the numbers were similar.

Good catch it should be 386 my apologies hopefully the op found the right ones

 

[chas036]

I had the same problem my A and it turned out to be the condenser. I ended up switching to electronic ignition and have never had a problem with ignitions again.