NAA missing when warm

BrazilBilly · Jan 13, 2019

I got my NAA out yesterday to grade some snow. It started fine, but once it warmed up it started missing. I suspected ignition coil as I have read on other posts, but I can get the engine to run smoothly by choking it some. That would seem to be a fuel problem, but I am not sure where to look. As long as I have had the tractor, about 22 years, the carburetor has never been opened. I always add gas through a screened funnel, the gas tank looks to be clean inside. I haven't opened up the sediment bulb to inspect the screen, but the bulb doesn't have any visible debris in it. Any suggestions would be greatly appreciated!

Thanks

Janicholson · Jan 13, 2019

A warmed up misfire that the choke helps could be a loos, cracked, or bad intake manifold gasket. AS the engine warms, the difference in temp can open up a vacuum leak. When warmed up, take a propane torch, with the end nozzle off, and with it running, wiff some propane near the intake manifod. (do this outside) if it changes, and starts to run on all cylinders you have found the issue. Jim

David G · Jan 13, 2019

Did it do it next time, if not could be carb icing.

Janicholson · Jan 13, 2019

Not a flame. Carb icing almost always make an engine very rich. (plugs up the venturi, not the fuel) Jim

David G · Jan 13, 2019

Ah, yes

Royse · Jan 13, 2019

Check the quality of your spark when it acts up. Should jump a 1/4 inch in open air.
I know it seems like a fuel problem, and it may be, but checking spark is free.
When was the last time the points were cleaned and adjusted?

leroy in ne · Jan 13, 2019

Thought, pushing snow, snow melting on distributor cap and or plugs and wires = miss. rich mixture as in partial choke will some times fire easier. Sometimes a cheap fix for this is spray cap inside and out with with WD-40.

Geo-TH,In · Jan 14, 2019

Here is how I prevent carb icing.

My Jubilee was running like carp. No power. New points and condenser solved the problem.

jimg.allentown · Jan 14, 2019

When an engine starts missing, that means that only one or two cylinders are affected.
Forget the things that will affect ALL cylinders.
Coil - will affect ALL cylinders.
Points - Also will affect ALL cylinders.
Carburetor - generally will affect all cylinders.

Now, look at the things that will affect ONE cylinder - Distributor cap, plug wires, valve adjustment.

Running too rich or too lean can cause the weaker cylinders to misfire before the stronger ones.

In the long run, it will pay you to do diagnostics before you start changing parts.

BrazilBilly · Jan 14, 2019

Thanks to all for reading and replying! I now have some things to check out and try. I will let you all know how this turns out.

BrazilBilly · Jul 14, 2020

Well, 18 months later I got back into this problem. During nnalert related downtime, I replaced the manifold. It did have a crack in it. I also replaced the distributor cap and points and verified plug gaps, all looking fine. I get about 3/8" spark jump from coil wire to ground when I check that. The tractor started right up and ran fine. I bushogged for about an hour with no issue and then began to miss, a little at first increasing to the point it wouldn't start and run. I bought a carburetor kit for the TSX428 carb, and reinstalled the carb. The tractor will only run if the choke is feathered nearly closed, never really running smooth.

So, I believe it is a carb issue now, but I am stuck as to where to look. Any ideas?

Thanks

NAA missing when warm

BrazilBilly

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Janicholson

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David G

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Janicholson

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David G

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Royse

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leroy in ne

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BrazilBilly

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