Farmall Cub

Having trouble starting tractor. When starting the tractor I turn on the switch, advance the throtle about 1/3 and pull the starter and pull the choke. Starter does its job but does not fire. After 2 or 3 tries, I pull the throtle back to minimum. I try again but when I let go of the starter there is a single cylinder firing. If I can respond quick enough and advance the throtle only one or two notches it sometimes will fire to more cylinders. After it has been running (warmed up) it most often will start normally. About 2 years ago, I changed the electric system from 6 volt to 12 volt, but I had to install an "Exciter Button" and everything has worked fine until about 6 months ago. Now I have to re-charge the battery before starting. I can't find anything wrong. Any help would be appreciated.
I hope I did this right. This is my first time posting anything.

its possible that you have some sticking valves (old gas). I had one do the same thing and found that the valves were sticking enough to cause these issues and once it "did" start it would run ok. then once it sat for a while and cooled off, the varnish would set up again and valves would stick. I put some seafoam in the engine oil and fuel tank.
ran it for awhile and problems ceased. just a thought.

Need more information on the "exciter" problem. Alternator used? How wired? Following is a link to a common Delco 10SI alternator conversion. Battery discharging is a common fault in that the wires are mixed up on terminals 1 and 2 - and or a diode or resistor not used in the #1 terminal wire.

http://s101.beta.photobucket.com/user/f ... sort=4&o=3

Hard starting problem. Complete engine tune up including compression tests and valve tappet adjustment.

Edit: Charging battery problem. Charge up battery and have checked at auto parts store. If battery is still good you will need to start checking for a short, the battery drain, when engine not running. Previously thought "exciter" button was not disconnecting after energizing alternator, which still could be the problem.

Question. Did you install a resistor in line with the coil, or coil with internal resistor, when converted to 12 volts?

too much choke? if everything's to spiff it doesn't take much if any
to fire set at a quarter throttle and no choke... my 6v '51 anyway.

ymmv depending on lower temps than mid winter ca...mid 40s

Would sound like Eugene has it nailed.

My guess is a compression problem, valves or rings. Perform a compression test. As stated, it many only be sticking valves or the valves may need adjusting.

Welcome to you in Michigan! Sorry to hear of your starting issues, but you've come to the right place and sounds like you're already getting sound advice.

Again, welcome to the forum! Don't forget to check out the "Manuals" link(s) above for a wealth of information.

hayseed235 wrote:when I let go of the starter there is a single cylinder firing

This suggests that there is a problem in the ignition system. It could be that there is not enough current getting through to run both the starter and give enough to the coil for a spark. Or, there could be a problem in the ignition system itself (points, condensor, etc.) When the starter stops drawing, then you get a good enough spark, or enough current to overcome a weak ignition component.

I had these symptoms more than once. One time it turned out to be a weak battery, another time it was old plugs.

Longshot... Intake manifold loose, bad gasket or cracked manifold.

Starts when throttle is almost closed denotes lean mixture so less air is needed attain proper mixture.

Once engine is eventually started, once warm it will start normally. Symptoms of all three of the aforementioned.

If you have no loose wires you most likely have a bad alt. A tune up and carb cleaning will most likely cure the starting problem
This is based on the info you have given
Boss