Starts right up on choke. then run inrun position for a minute and have to go back to choke to keep it running ,then it runs fine for a couple of minutes and have to go back to choke and start all over again.

i dont know nothing about the cub cadet but if its doing that i would change the camshaft positioning sensor

First , prime the priming bulb about 4 x...

Next put the choke lever in full choke position

Give a couple slow pulls, then a good strong pull...

(The unit should burp, run for a second)

Next put the choke lever in the half choke position

Pull rope

It should start and run, now put the choke lever all the way in the off position and let unit warm up a minute... if when you turn choke off it stalls out, u didn't warm it up enough...

indicates that the auto choke ( carby ) needs adjusting or if fuel injected , the ambient temp sensor needs replacing

Instructions

1. • 1 Locate the red button on the top of the handlebars. This is called the "kill switch." When you pull it up the engine can run; when you push it down, the engine will shut off immediately.
     
   • 2 Pull the kill switch up.
     
   • 3 Turn the key to the "on" position.
     
   • 4 Make certain the cord running from the key is attached to the steering column. This device acts in the same manner as the kill switch - the engine will run only when it is secured.
     
   • 5 Pull the start cord, which looks like an enlarged lawnmower pull-cord and is generally found on the right side of the machine.
     
   • 6 Listen to the engine - if it starts, let it get going slowly . If it "pops" but does not continue to run, try pulling the start cord a few more times. If you do not hear the engine turn over at all, proceed to the next step.
     
   • 7 Find the pull tab under the right side of the handlebars. This is called the choke - it often has a circle with a diagonal line through it. The choke helps to start an engine when the weather is very cold or the machine hasn't been used in a while. When using the choke, try leaving it on only long enough to hear the engine fire a couple times, then return it to the "off" position. A choke left on too long can flood the engine.
     
   • 8 Place the choke in the vertical position - this is called the half choke position. Pull the start cord several times. If the engine fires up, place the choke back down to its original position and let it slowly warm up. If the engine still has trouble starting, proceed to the next step.
     
   • 9 Pull the choke 180 degrees from its original position - this is called the full choke. Pull the start cord until the engine sputters a couple times.
     
   • 10 Replace the choke to the original off position and continue to pull the cord. The engine should fire up and settle into a steady hum, ready for fun in the snow.
     

Instructions

1. • 1 Locate the red button on the top of the handlebars. This is called the "kill switch." When you pull it up the engine can run; when you push it down, the engine will shut off immediately.
     
   • 2 Pull the kill switch up.
     
   • 3 Turn the key to the "on" position.
     
   • 4 Make certain the cord running from the key is attached to the steering column. This device acts in the same manner as the kill switch - the engine will run only when it is secured.
     
   • 5 Pull the start cord, which looks like an enlarged lawnmower pull-cord and is generally found on the right side of the machine.
     
   • 6 Listen to the engine - if it starts, let it get going slowly . If it "pops" but does not continue to run, try pulling the start cord a few more times. If you do not hear the engine turn over at all, proceed to the next step.
     
   • 7 Find the pull tab under the right side of the handlebars. This is called the choke - it often has a circle with a diagonal line through it. The choke helps to start an engine when the weather is very cold or the machine hasn't been used in a while. When using the choke, try leaving it on only long enough to hear the engine fire a couple times, then return it to the "off" position. A choke left on too long can flood the engine.
     
   • 8 Place the choke in the vertical position - this is called the half choke position. Pull the start cord several times. If the engine fires up, place the choke back down to its original position and let it slowly warm up. If the engine still has trouble starting, proceed to the next step.
     
   • 9 Pull the choke 180 degrees from its original position - this is called the full choke. Pull the start cord until the engine sputters a couple times.
     
   • 10 Replace the choke to the original off position and continue to pull the cord. The engine should fire up and settle into a steady hum, ready for fun in the snow.
     

The black smoke and black spark plugs indicate that the engine is running very rich (ie too much fuel). This could be caused by the choke not opening fully after the engine starts and the fuel mixture is too rich OR the fuel mixture setting is opened too far.
Check the choke lever, make sure the choke is fully open when the choke is in the running position.
When the engine is running with the throttle is in the 3/4 rev position then adjust the fuel mixture to get the highest RPM.

Try changing your fuel filter and also clean the air filter too. the machine is starved for fuel

Carburetta is fouled. Run fine on choke - rich mixture. As it warms up and choke pulls off, its starving for gas.
First try adding fuel system cleaner to the gas tank. Do NOT go overboard. No more than double the recommended mix ratio.
The alternative is to remove the carb, open the bowl and spray out the jets and venturi with carb cleaner.

Its possible you may help it by removing the air filter and spraying every orifice you find on top of the carb. With carb cleaner. Be very carefull not to flood, pool carb cleaner in intake as this is not healthy for engine either. You can do this with engine running, so as not to pool, but slowly is best, both in engine speed and volume of carb cleaner.

Sounds like a carb issue. Try spraying carb and choke cleaner while it is running. If that does not help may be remove carb and clean and rebuild it. My weed eater does same thing and I get it running and then spray it down. It takes a couple of sprayings but it helps.

Good luck
roundo4

ahter you start it up turn choke too off position