Farmall H backfiring

Gregg Anderson · Dec 30, 2008

I have a 1952 farmall h and it does not want to run right. It starts but it is constantly backfiring. I have replaced the plugs, wires, coil, cap and rotor. I have also cleaned the carb and changed the gas to make sure it was not bad. Was wondering if anyone had any ideas what could be going on.

old · Dec 30, 2008

Back firing is caused by one of 2 things. #1 the carb maybe set to lean or has a clogged main jet or #2 the timing is off. Well maybe 3 things. Valves set to tight will also cause that problem
Hobby farm

Gregg Anderson · Dec 30, 2008

Thanks for your help

Janicholson · Dec 30, 2008

I'll add to Old's comments that a consistant backfire can be caused by a crack in the distributor cap allowing spark to be sent to the wrong cylinder.
An intake valve leaking burning gasses back into the intake track.
Spark plug wires on the wrong terminals--
Should look like this from rear looking forward:
2-1
4-3
Front plug is #1
A bad spark plug Dead missfire can backfire if unburned fuel gets into the exhaust manifold
A leaky intake manifold will run one cylinder so lean that it backfires and runs rough.
Check as follows.
While it is running, pull off one spark plug wire at a time (use insulated pliers or get shocked!!) If there is one cylinder not changing the speed, it is an issue. Swap spark plugs with that one and see if things get better, or follow the plug. Change that plug if it follows to be sure.
Compression check. Good gauge charged battery, all plugs out, throttle open. Good luck. Keep us involved. JimN

Anonymous-0 · Dec 30, 2008

If you feel comfortable that you have ruled out all things electrical & ensured that it is timed correctly, check the following: Distributor gear, Compression check of each cylinder, then with the motor running - remove valve covers - ensure proper functioning of valve springs & push rods. You might find the problem here in the top end of the motor - and need an overhaul............

Anonymous-0 · Dec 30, 2008

My 45 started doing that this year. Always ran perfect then one day it didn't run too good and was backfiring. I loosened the valve cover and lifted it up and one of the pushrods had come out from under the rocker arm. I figure the valve must have stuck and allowed the rod to come loose. Runs perfect now.

Janicholson · Dec 30, 2008

One more item. If the distributor shaft is worn and the rotor shaft and 4lobe cam wobble it will do that exact misfir and backfire operation. If you can wiggle the distributor shaft (side to side) at all visibly, it is toast and needs a new distributor bushing. JimN

El Toro · Dec 30, 2008

Open that main jet adjusting screw near the bottom of the carburetor and see if that helps. Take a good look at the cap for any hairline cracks. Hal

Red Mist · Dec 30, 2008

And, if the governor has frozen up, it will backfire, especially when you give it throttle. mike

Farmall H backfiring

Gregg Anderson

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old

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Gregg Anderson

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Janicholson

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Anonymous-0

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Anonymous-0

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Janicholson

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El Toro

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Red Mist

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