# runs fine cold, hiccups when hot



## old lo-boy (May 6, 2009)

My international cub, a 12 volt system!!, starts easily and runs fine for about 2 minutes. Then when I'm using some power it begins to surge several times and eventually dies.
If I wait a couple of minutes I can repeat the same events. What is the diagnosis, please??

I have rebuilt the (tiny) carb, bought a new coil, dist cap, rotor.

I did get the engine too hot last year, mowing fast in the heat; I think the trouble began that day.

This is a cub lo-boy tractor. serial #204652. don't know the year.


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## Live Oak (Dec 22, 2003)

Sounds as if the engine is being starved out for fuel. By chance have you replaced the fuel cap with the recall replacement vented fuel cap? This may or may not be the cause. (I kinda doubt it but it would good to replace it) 

Have you checked the inside of the fuel tank for crud that could be stopping up the fuel pickup at the bottom of the tank? 

Another possibility is electrical. Does your ignition system have an inline resistor before the coil? These resistors look like a piece of white ceramic block with a metal coil inside. The coil can sometimes get hot and crack. When it cools off it makes contact again and the engine starts right up but after a few minutes the resistor coil gets hot and expands and the crack opens up......the engine quits. 

Lastly, check the carb. fuel inlet valve. It may be stuck and only letting in a small amount of fuel. Enough to start and run for a short time but not enough to keep the carb fed. 

Welcome to Tractor Forum by the way! :cheers:


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## old lo-boy (May 6, 2009)

Thanks for the tips. I haven't found an external resistor. The coil grounds right to the dist. and the hot wire comes out of the wiring harness so I assume, no resistor. The replacement coil does have an internal resisitor (bought at Car Quest) and seems to work. I will try the gas cap trick by loosening it for a test. When I remove the fuel line from the carb I get a good stream of gas from the line. I found and installed a carb. kit, but I could walk along beside the tractor and spary instant start into the carb when it acts up! I should try to figure if it is lack of gas before I buy more parts. Thanks again.


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## old dog (Jul 14, 2009)

Don't know if this will help. I had a simular problem--gas would flow through gas line when unhooked from carb. When running it woud shut down (my IH T-340 crawler). The only way to get it running again was to blow through gas line. Because old line was so short, I put a new longer line so I could reach it easier. Well end of problem--think old line may have restricted flow when hot. Shot in the dark-hope it works for you


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## Leon (Jun 23, 2009)

I vote for fuel restriction. Pull the pipe plug out of the bottom of the carb and see if you get a constant supply of fuel or if it guzzles out and then slows to a trickle. Install/replace the plug a couple of times, if it guzzles then trickles each time, your float, needle valve/seat or the metal screen on the carb are causing the problem.

-Leon


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## caseman-d (Nov 29, 2003)

I say you may have a hole in your intake manifold and sucking air. In most cases sucking air is good,, not true here. With manifold is cool and tractor running spray starting fluid and see it changes tune.
caseman-d


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## SCPOret (Oct 24, 2009)

*Cub*

No one has mentioned the governor. Your throttle actually sets the governor which, in turn, operates the carbureator. If your governor is sticky then it will be erratic in operation.

You didn't mention if you had checked the screen in the top of the sediment bowl, if it's partially plugged it can cause the run fine and sputter out condition.

Your serial number would indicate a 1956.


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## old lo-boy (May 6, 2009)

Thanks for your suggestions. The tractor runs fine now--IF I keep cold water near the carb. so it stays reasonably cool!
The problem was entirely "gas related". I did need to clean the carb. & install a fuel filter. but, it seems the carb. is warped, or more accurately does warp when the carb. gets hot & the gas doesn't atomize properly then. 
But, now, I can use the tractor freely when the air temp. is below 60 degrees & if it is above, say, 75, I need a small water bath at the carb. to keep it cool. I use a customized half-gallon milk jug for this, wired up under the carb.
Old -Lo-Boy


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