1950 John Deere Model A doesn't want to run right

Spalding6693 · Oct 19, 2016

Hey everyone. I've been having trouble getting my 1950 model A to run. I've done all the work I thought I needed to do. When I got the tractor I rebuilt the governor and replaced the bearings, and same for the fan shaft. I put all new wirING ok it except for the starter cable. I also put a ditributor point system on it. I had the head and valves done, and the block bored over with new pistons. I noticed though when I was putting the piston rods on the crank that I had two number 2 piston rods. I figured there was no difference between the lengths or anything so I put them in. Be for I took the block out I had the tractor timed up, and the throttle rods to there correct lengths as they say in the book. I've even put two different rebuilt carbs on it. So now that everything is on there when I go to start it, it will usually fire right off, but after like 4-8 seconds later it will start to stall out and the throttle valve will pull on the governor and it will either backfire or stall out. If anyone has any idea of what it could be please let me know thanks.

Waterloo · Oct 19, 2016

Are the New Pistons Aluminum? I have rebuilt several two cylinder tractors having the blocks bored and installing new pistons. The specs for aluminum pistons are different than the original cast pistons. The aluminum pistons typically require 0.012 -0.015 clearance while the original cast pistons only required 0.008 - 0.009. When the tractor starts to heat up the pistons enlarge greater, being aluminum. One parts provider I have used for many years stated he was aware of cases were the aluminum pistons ceased to the cylinder walls and locked the engine down. He gave fare warning on the first set of aluminum pistons I purchased from him. If you like you can contact me (Bruce) at 864-933-5073

Spalding6693 · Oct 19, 2016

(quoted from post at 05:49:33 10/19/16) Are the New Pistons Aluminum? I have rebuilt several two cylinder tractors having the blocks bored and installing new pistons. The specs for aluminum pistons are different than the original cast pistons. The aluminum pistons typically require 0.012 -0.015 clearance while the original cast pistons only required 0.008 - 0.009. When the tractor starts to heat up the pistons enlarge greater, being aluminum. One parts provider I have used for many years stated he was aware of cases were the aluminum pistons ceased to the cylinder walls and locked the engine down. He gave fare warning on the first set of aluminum pistons I purchased from him. If you like you can contact me (Bruce) at 864-933-5073

I brought the Pistons to the machinist that bored it out so he could get the measurements for the bore. So I'm thinking it can't be that. Thanks for you advice though.

PopinJohn · Oct 19, 2016

Do you have the carburetor set for starting?
1-? turns out on the IDLE mixture.
1 turn out on the LOAD mixture.
Sounds like starving for fuel.
IDLE does not mean slow RPM, it means no-load mixture at any RPM.

ss55 · Oct 19, 2016

Kinda sounds like the idle circuit in the carburetor is mostly plugged up so it's only getting fuel when the governor opens the throttle enough to open the main/power circuit.

If it only fires when the starter is engaged it could be a bad ballast resistor on the ignition.

Spalding6693 · Oct 19, 2016

(quoted from post at 07:04:46 10/19/16) Do you have the carburetor set for starting?
1-? turns out on the IDLE mixture.
1 turn out on the LOAD mixture.
Sounds like starving for fuel.
IDLE does not mean slow RPM, it means no-load mixture at any RPM.

The carbs I used were set up for starting. I rebuilt the one that came with the tractor witch turned out to be junk, and I bought a rebuilt one that was all set up. 1 and a quater turn for idle and 1 turn on the load. The float is also at the correct measurement. I also fiddled with the idle to see if it would run any better and neither way worked.

Spalding6693 · Oct 19, 2016

(reply to post at 08:01:17 10/19/16)

The carbs I used were all rebuilt by two different places. So they should be all cleaned. Also I don't think it has anything to do with the resistor because be for I took the block and head out to have it redone that tractor was running. It wasn't running great, but I could put a load behind it.

brutus49DC · Oct 19, 2016

you have to adjust the carb on the tractor while running, you can't just buy a carb that is pre adjusted and ready to run, on a side note I had a 39a once that I bought and got running, I told my dad I thought it was missing, he lookled at me and asked,"how could you tell?"

Spalding6693 · Oct 19, 2016

(quoted from post at 09:26:01 10/19/16) you have to adjust the carb on the tractor while running, you can't just buy a carb that is pre adjusted and ready to run, on a side note I had a 39a once that I bought and got running, I told my dad I thought it was missing, he lookled at me and asked,"how could you tell?"

I understand that you have to adjust the needles while it's running I've turned the idle needle every witch way and it doesn't seem to make a difference. I had my father and uncle down there ( that have a handful of two cylinders too ) and they played around with the carb too and got nothing out of it.

old · Oct 19, 2016

If you choke it does it help or hurt?? Do you get black smoke or little or no smoke?? Have you made sure the air cleaner is not clogged up and have you changed the mud and water in it??

A lot of times a back fire is to lean a carb setting and if that is so choking it should in theory help

teddy52food · Oct 19, 2016

Did you close the load needle when adjusting the idle? If so the carb needs work.

Mark-Ia · Oct 19, 2016

I don't think you have enough fuel flowing out of the tank to the carb.

RandyB(MI) · Oct 19, 2016

Find a neighbor/friend with an A or B or even G and try those carbs out on a known good running tractor. I think you will discover your problem is two carbs done wrong.

MSD · Oct 19, 2016

Bad condenser will fool you into thinking it is carb troubles.

MSD · Oct 19, 2016

A bad condenser will fool you into thinking it is carb troubles.

Leroy · Oct 20, 2016

That tractor should have had a mag when new and the distributor conversions DID NOT USE a resistor. Have had both A & B with the conversions and NO resistor.

1950 John Deere Model A doesn't want to run right

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