1020 backfire thru carb and exhaust

3cylgas · Feb 10, 2013

Recently installed electronic ignition into my tractore that had no spark due to a mess under the distributor cap. Plenty of spark now. Removed carb, took apart, cleaned and reinstalled. Now tractor backfires thru exhaust and spits out thru air intake. I have drained fuel tank as well. It will run but have to hold your mouth right and not well enough to pull itself.

old · Feb 10, 2013

Good chance the timing is way off and the carb maybe set to lean. I learned years ago fix one problem at a time and make sure you have it right before trying to do more. Called trouble shooting before throwing parts at it

showcrop · Feb 11, 2013

I have to agree with my mentor young fella Old here, chances are timing is way off. i have two nearly identical Ford 172s here. One has points, the other a Pertronix. The distributor position is very different between the two.

ericlb · Feb 11, 2013

it might also be easier to just fix the 'mess' under the cap and keep the tractor the way is was made i grew up on point style ignition systems there just not that hard to understand, once you go to electronic sure you dont have to change points anymore but then you wind up chasing problems down all over the engine and when the electronic system fails your dead in the water requiring a trip to town and some pretty good money to get it going,when points fail its 15 minutes to put in another set and your running again, you umm keep a spare set of points and condenser in the tool box like i do right

rrlund · Feb 11, 2013

If it backfires through the carb it's one thing,if it backfures out the exhaust it's the other isn't it? One way is ignition,the other way is fuel? I don't remember which way is which. Can you remember Rich?

buickanddeere · Feb 11, 2013

Ensure the rotor is lined up with the towers on the cap when it's time to fire.
Use solid core plug wires and 3116 non resistor plugs. iirc some electronic conversions require at minimum a high voltage resistor wire between the coil and distributer Don't over gap the plugs too wide.
Anybody ever check the valve lash?

Bob M · Feb 11, 2013

A couple more things to look for:

Check/reset valve clearances and check for an intermittently sticking valve(s).

Verify timing with a timing light. If the timing is not steady (mark moves more than a couple degrees either side of spec at idle) there's a problem with the distributor. Look for a worn distributor shaft bushings or a broken centrifugal advance.

old · Feb 11, 2013

Exhaust is most of the time from the timing being off. Back fire out the carb then carb set to lean

rrlund · Feb 11, 2013

So if this one's spitting back through the intake most likely the carb then not the ignition then right? Would seem to me he's got that problem licked with the electronic ignition.

old · Feb 11, 2013

Ah but if the ignition timing is off that can cause many funny things and the new electronic system is not always all that is it cracked up to be

Jerry/MT · Feb 12, 2013

Check the ignition timing and the centrifugal advance function. Your timing may be retarded.

Randysouthmississippi · Feb 21, 2013

You didnt by chance cross two of the plug wires did you.

1020 backfire thru carb and exhaust

3cylgas

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old

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showcrop

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ericlb

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rrlund

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buickanddeere

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Bob M

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old

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rrlund

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old

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Jerry/MT

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Randysouthmississippi

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