John Deere 2020 backfires

[JCS Wood]

I just got a 2020 gas and when cold it turns over and starts but will backfire frequently until it warms up. Any ideas? Also, found online point gap and plug gap specs but can't find proper plugs to use. Has Autolite 66 plugs in it now.

 

[wore out]

I just got a 2020 gas and when cold it turns over and starts but will backfire frequently until it warms up. Any ideas? Also, found online point gap and plug gap specs but can't find proper plugs to use. Has Autolite 66 plugs in it now.

It possibly could be running a little lean.

I would check point gap, centrifugal advance function, timing, and the condition of the cap and rotor, sparkplug wires, and sparkplugs.

Parts catalog shows PRESTOLITE 14G3, CHAMPION N-11Y, and CHAMPION N-6 sparkplugs.

https://partscatalog.deere.com/jdrc/navigation/equipment/3229

 

[Jim.ME]

NGK 7734 sparkplugs should work as well

 

[JIM MN]

Could it be a sticking intake or exhaust valve when cold, but frees up when all warmed up? You may recheck the points gap. May have changed? Also, get a power timing light, and check the ignition timing?

 

[JCS Wood]

Thanks for the quick replies. Ordered new plugs- but fired it up with old plugs in today. Ran kind of wimpy until it warmed up (no backfiring) and then did about 2 hrs. of chisel plowing food plots. Didn't miss a beat. So I'll do an oil change, check the points and timing and tear into it. Maybe old gas had something to do with it also? I put high octane in it- would a tractor from 1969-70 need lead additive?

 

[wore out]

Thanks for the quick replies. Ordered new plugs- but fired it up with old plugs in today. Ran kind of wimpy until it warmed up (no backfiring) and then did about 2 hrs. of chisel plowing food plots. Didn't miss a beat. So I'll do an oil change, check the points and timing and tear into it. Maybe old gas had something to do with it also? I put high octane in it- would a tractor from 1969-70 need lead additive?

It doesn't need "lead additive" and it certainly doesn't need "high octane gasoline".

 

[Limestone]

I would switch over to electronic ignition if it were me.. carb may need a cleaning/rebuild, where I buy my gas they have 90 octane straight gas, i use it in all my gas powered engines, especially the tractors.

 

[Fixingfarmer]

I would switch over to electronic ignition if it were me.. carb may need a cleaning/rebuild, where I buy my gas they have 90 octane straight gas, i use it in all my gas powered engines, especially the tractors.

Checking the timing before converting especially if it runs at all is the rule here. Use timing light. If it runs good on points then spend the money. Cleaning the carburetor as you suggest might help as well green ones do have a tendency to backfire when super lean 2 cylinders especially i assume it’s more vapor is hanging around longer nothing to push it out as fast like if there were 2 more pistons with 2 more exhaust strokes. I don’t run the carb empty for that reason during the summer if anything I dump it out with the manual screw.

Also wouldn’t be a bad idea to adjust the valves. They will tighten as they run and that could be part of the issue. I never understood how exactly if the seats are what wears down more then the stem but the old guys always said don’t overtighten the screw you should have some drag on that feeler gauge.

new plugs gapped correctly once they arrive would be the next thing to try.

 

[ss55]

It possibly could be running a little lean.

I would check point gap, centrifugal advance function, timing, and the condition of the cap and rotor, sparkplug wires, and sparkplugs.

Parts catalog shows PRESTOLITE 14G3, CHAMPION N-11Y, and CHAMPION N-6 sparkplugs.

https://partscatalog.deere.com/jdrc/navigation/equipment/3229

If it runs better with a little choke then the idle passages might be partially plugged.