I would check the following

(for safety's sake be sure to disconnect the negative- battery cable before doing the following)

1) The cable and clamps from the battery to the solenoid and the cable and clamps from the solenoid to the starter.

Remove then and scrape/sand them clean and rub them down with a bit of WD-40 and reinstall.

2) Give the negative cable from the battery this same treatment. Be sure the chassis end of this cable has a good connection to BARE metal.

3)Make sure the solenoid is tightly anchored to the chassis. Ideally take it off an make sure there is bright shiny metal on the engine and solenoid to assure a good ground connection.

Be sure to make the last connection point in reassembly is the - battery connection.

Let us know if this helps, and we can give you the next steps if necessary.

Are you sure it is running on BOTH cylinders?

Besides the suggestions in above post, I have a list of possible causes of difficulty starting this engine, a common complaint.

Walt Conner
wconner5 at verizon dot net

Thanks for the advice I will try these suggestion this weekend.

Can not run tractor past fast idel, engine cuts out just past half idel speed.

Please tell us what the engine model number and type number are. If we know the identity of the engine, it will permit a more accurate response.
What you have said so far suggests that your carburetor is in dire need of a thorough cleaning.