NAA Running rough after 1 hour

KrisNMo · Feb 3, 2013

I've this problem since I've had this tractor for about 8 years now. This tractor has new a fuel tank, new prebent metal fuel line, fuel tank valve, all new fuel filters, new 437 plugs, points, condensor, plug wires, carburetor rebuilt, 12 volt coil, new 12 volt alternator, complete new wire and key switch. Starts just great, Runs great for about an hour then it starts run rough and I have to run it with about 1/3 choke to smooth out until I'm done working the tractor. Today while plowing snow it started running rough again after about an hour and I had to once again run 1/3 choke until I was done plowing 30 minutes later. I've tried adjusting the carburetor but it has no effect on how it runs when it's running rough like this. I am out of ideas now because it's run like this since before I changed all the above. I never changed everything above because of this problem. Changing all the above was just to know I had everything new and hopefully have no problems while plowing snow. Any ideas would be appreciated.

JF in MI · Feb 3, 2013

Have you tried running it with the fuel tank cap off?

KrisNMo · Feb 3, 2013

Haven't tried running it with gas cap off yet, but it does have a newer vented cap I traded into the New Holland dealer about 6 years ago. I'm going to try this the next time it acts up.

I was just talking with a neighbor and he was thinking maybe a worn distributor or timing is off. But I would think if it was a distributor problem it would run rough as soon as it started running?

old · Feb 3, 2013

When was the last time you serviced the air cleaner?? Next check spark when it acts up as in the spark need to jump a 1/4 inch gap or more. Also check the coil and see if it is so hot you can not touch it if it is you may have a bad coil yes I know it is new so what can still be bad

Traper · Feb 3, 2013

Kris
If nothing seems to work add 1qt 2cycle oil to full tank of fuel.Have seen valves hang in guides when hot if tractor sat alot before you aquired it
Traper

KrisNMo · Feb 3, 2013

(quoted from post at 14:10:17 02/03/13) When was the last time you serviced the air cleaner?? Next check spark when it acts up as in the spark need to jump a 1/4 inch gap or more. Also check the coil and see if it is so hot you can not touch it if it is you may have a bad coil yes I know it is new so what can still be bad

Old, Don't you think it would be the other way around and not enough fuel since I have to close off the choke 1/3? Tells me I have good spark and not enough fuel or too much air? Am I thinking wrong or over thinking this?

Maybe the float set too low in the carburetor? Thinking outside my box.

old · Feb 3, 2013

Weak of poor spark will look like a fuel problem and the hour says coil is heating up or some other thing in the ignition system. Or if the air cleaner is empty as in no oil then after a while it may stave for fuel due to lack of restriction that the air cleaner will give

agd2perf · Feb 3, 2013

Get rid of the pre-bent fuel line, it sounds like it is vapor locking. Get a piece of brake line, and go straight to the carburetor, (no fancy turns or curves)where it can heat up. This should fix your problem, I had the same problem with my 600 series.

joe201 · Feb 3, 2013

have a NAA that would run great for 45 min then die. let set 10 mins pull out choke and restart and run with choke out a little. Ran it like that most of one summer, found junk in gas line elbow on caburetor.

Royse · Feb 3, 2013

What does your temp gauge say at that hour mark?
Any water in the oil or oil in the radiator?
A non-vented gas cap on my tractor kills it in just a few minutes.
Same as leaving the the fuel turned off.
I don't think the fuel line would do it either, not in that time frame.
Old's idea of checking spark right when it fails is good advice.
If nothing else it's free and rules that out as a possibility.
And yes, weak spark will run better with the choke partially out.
Have you done a hot or running compression test?
I'd be interested in knowing what you find.

Texasmark1 · Feb 4, 2013

I wouldn't entirely omit spark. An overheated ignition coil could
produce that problem if an incorrect ballast resistor was employed.
The requirement to add fuel could be "an engine's excuse" to
overcome misfiring cylinders.

A quick check with a timing light would answer the question. Just
walk it down the spark plug wires from front to rear to see that they
are all firing evenly.

Mark

Steve (Tx) · Feb 7, 2013

Agd2Perf"s vapor lock possibility may be the answer.

I had similar problems with my 641. The solution in my case was to reroute the fuel line to minimize the exposure of the fuel line to the hot exhaust manifold.

Where the fuel line was close to any hot engine parts, I wrapped the line with aluminum foil. Problem solved.

KrisNMo · Feb 8, 2013

I'm pretty sure that vapor locking is my problem after reading a lot of postings I found here and in other forums plus with the help of you guys here. I think I found a fuel line sleeve product that may just work for my problem but only time will tell after I get it on and tried out. And this product comes in different colors including red.

http://www.jegs.com/i/Taylor/895/2580/10002/-1?parentProductId=946133

NAA Running rough after 1 hour

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old

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