Stalling Ford 640

Hey All,

I have a Ford 640 with a Zenith carb on it. I took it off after it had been on for about a year to clean it out. Now that the carb is back on the tractor it won"t stay running. I start the tractor (I don"t even need to choke it to get it started)and it will sit and idle with the trottle at any speed just fine for 3 or 4 minutes then it stalls. Just before it stalls I can see the trottle linkage move by itself. The trottle lever up by the steering wheel doesn"t move.If I go to start it again it will start right up and do the same thing. I can keep the thing running by choking it but only for a few seconds longer. There is only one adjusting screw on the outside of the carb. It"s the idle adjustment. I"ve set it back to the factory spec. (1 1/2 turns).I"ve had to adjust that out a bit but no matter where it is it doesn"t seem to change the tractors behavior.
I just can"t seem to figure out why that trottle linkage is moving on it"s own and when it does it shuts the tractor down. Oh I do see gas in the float bowl at all times. I"m in Texas so the tempature is usually in the mid 70"s this time of year. The tractor acts this way when I first try it and it"s been sitting cold or the 20th time I start it and it"s gotten warmed up.
Any ideas would be a great help.

Thanks

Rick

1.) The throttle linkage moves as it stalls 'cause the governor senses the loss of engine speed as it's stalling and opens the carb butterfly to try to compensate. COMPLETELY normal.

2. It is either stalling from lack of fuel (restriction somewhere) or lack of spark... could be a bad coil or condensor. You need to get a spark tester on one of the plug wires and watch the spark closely. When it starts to die, does it lose spark or does it continue to have spark 'til it coasts to a stop... checking that will narrow the problem down to loss of spark or loss of fuel.

Sounds like something in fuel line or cap not venting, pull line off at carb and make sure you get enough gas and it keeps flowing for 4 or 5 minutes

If you have a bowl strainer, you could have put the fuel supply fitting (the one the bolt goes through) on backwards. It has an internal channel that lines up with a fuel port in the bolt. If you put it on backwards, the hole in the bolt doesn"t line up with the channel in the fitting and you get restricted fuel flow.