John Deere A starts hard, misfires intermittently under load

Looking for some advice on my 49 A. I bought the tractor last summer at which point it had filled the crankcase with gasoline. I went through the carburetor and put new points cap condenser rotor wire on the mag. She runs real nice about 95% of the time. However, theres 3 things she does that are odd to me that I am trying to troubleshoot:


1) Starts hard. She spins over fine and pops off but doesn't start right away. She'll sit there for maybe 5-10 seconds going pop-pop-pop-pop until she finally runs regular. I though it might be a air restriction so I pulled the oil cup off and tried to start her but she sounded the same.

2)Misfires occasionally under load, sometimes severely. I was plowing last night (2x16 in clay) and she pulled the plow very well in 2nd gear. Never lugs down but occasionally she misses and sometimes misses successively, on one occasion killing the engine. There seems no telling when she'll do it though and she might go 20 minutes between misfires.

3.)Hesitates and makes a load pop almost like a backfire but not so distinct when she comes to the bottom of a hill and is about to start climbing another. She does the same thing when you engage the clutch rapidly without easing it in.


I will be trying to post some videos shortly. Thanks,


Pete

You will get many responses on what to check. If it were me, not knowing how you set the carburetor, I would try opening the load screw a full turn and see what that does. If it helps it may run too rich which you can always correct by backing off the setting a little at a time. I have a '51 AR that I have had problems similar to yours and found my condenser was at fault. Seems it is hard to get a good one anymore. Need to also make sure your condenser is clean and tight where fastened on the distributor.

My JD A pulling tractor acted the same way. Sometimes very hard to start, would run ok then misfire, sometimes just quit. Intermittent good then bad.
Replaced the coil and its been fine.

Well you still could have a fuel problem ? or an ignition problem ? Many times it is hard to tell which without a known good carb. or mag to swap out.
I once worked on a late AR. Guy had tried everything and had others work on it too. It would throw odd fits too. Turned out the cam was jumping around in it due to bad cam bearings. The left hand side seems to take the most abuse and is also the easiest to replace. I have had other A and 60 model since have the same issues. I can't say for sure that is your problem. But it is a remote possibility.

Never hurts to remove the air cleaner oil cup and push a GOOD stream of water up the inlet tube, to flush out Mud Dauber nests....just say-in..!!

Could be the Carb is ready for a REAL Re-build and/or weak ignition..(Probably BOTH)..

Could be your distributor bearings are loose causing irregular spark. Ron MN

it has a wico xh mag

I would pull the cover and check play in the mag too. Ron MN

ok thanks. I think I might pop the mag off tonight and take it to a guy I know who rebuilds them. He can test it for me

Would be good to know exactly what 'went through carb" means in detail. Your # 3 sounds like either load circuit plugged/vent plugged or throttle shaft binding . Watch the throttle lever on top of carb when you engage clutch. It should be opened up by gov rod to give more gas to get going. If it does move forward but tractor still bogs, then it's carb issue. If all is right in carb, open idle needle 1 1/2 and load 1 turn. If it doesn't work correctly there, you have carb issues. Will await your vid.

Randy, by went through the carb I mean this: first the only thing I needed to do to get it to run and stay running was drop the bowl, clean out the crud and replace the needle and seat. This stopped the aforementioned issue.

Later in the fall when I got the time to do it, I took the carburetor apart and soaked it in I think a diesel/gas blend for a day (not the professional way to do it I understand). Then I used the small drill bits from Robert's and followed their printed instructions. Then I sprayed carb generously in the orifices and blew out with compressed air and reassembled. Now, I did not replace the throttle shaft and bushings because they didn't seem too bad and I know you have to ream those bushings just right to let the governor control the shaft. I did remove the vent baffle and blew it out but I can't remember any more detail than that. The load setting is a generous turn out and the idle 1.5 turns.

With that being said, I'm no pro so the carb could very well be the issue. I am having a tough time getting any videos to load to this site (maybe my file size is too big). Anyone interested, I can email links of the misfire and the hard starting. My email is [email protected]. Thanks,

Pete

https://photos.app.goo.gl/FWajW1y9HbNZe15p7

https://photos.app.goo.gl/V7QUGyMkveLhY4B37

Yea...when mine do that, I figure they musta got MAD at me for some reason...

2-Cylinder JD's DO that sometimes..!!!

Actually, if it runs well most of the time, I would suspect Sparkplug wires and/or carbon (or moisture) in the Mag/Dist cover...we have had those problems often, anytime the have to be left in the field over night..

Many times they would just plain NOT start in the early morning and ( we had straight pipes on our Late Styled JD B's because they burned valves badly) the neighboring households would progressively be turning lights on as those 2 JDs Cranked and Cranked, with the loudest BACKFIRES you ever heard..!!

Some mornings, we had to wait until the morning Sun could shine into and on the opened Mag Cap and mag for a few minutes before they would start...

Seems not many remember those times with Mags...!!!

Otherwise, those mags are Still running and starting like new...as long as they are stored inside away from the moisture..

Here is one Treatment Dad used on our Late Styled JD B tractors every spring..

Warning...this may excite your neighbors..!!!

With the engine warmed up and running at about 1/2 throttle, remove the vent tube from the Carburetor and with a pump oil-can ( and good clean used oil),
Pump in all she can stand and keep running...(should free up and lube the valves)..

Probably a good idea to warn the local Fire Dept...she WILL smoke a "little"...

Could be this will help..certainly will not hurt anything...!!

Always quite a show when we did this to both of them..!!!

One detail I forgot to mention, when I put new plugs in last fall (autolite 3116s) I noticed that the plugs that a previous owner put in were mismatched. I think I still have them to check but maybe a previous owner had a similar problem and tried a hotter plug on the lazy cylinder? I spoke to an old Deere dealer from back in the day today and he suggested I run a compression test, he suspects valve burning out.

Tested compression on each cylinder tonight and with throttle open each cylinder showed about 105 psi from the best I could tell (its a CHEAP gauge though so I wouldn't put too much trust in it). I did notice that the clutch side plug was wet and darker than the flywheel side plug when I took them out. Should I try running a hotter plug say champion d21 or 23 in that side or an autolite 388? Not sure why one side would foul before the other with compression being equal from side to side. Pulled the mag cap and adjusted points. Looked clean and couldn't tell much wobble in the main cam of the mag, how much is too much? Thanks,

Pete