These tractors are pretty simple machines; itís usually pretty easy to get them running with some basic troubleshooting steps.
There are three approaches you can take:
1. Replace every part you can until it starts or you run out of money.
2. List every possible cause of the problem and then randomly pick your favorite to check. It could be your coil. Or your ignition switch. Or about 10 other things.
3. Like diagnosing any other equipment failure, take a step-by-step approach, working from the most likely to the least likely, one system at a time.
Iíve tried all three approaches. The third one always worked for me. Sounds like you are trying option # 1.
I might not be able to tell you why your tractor isnít running, but I can tell you how to figure it out for yourself.
You could have a spark issue.
You could have a fuel issue.
Donít guess. Troubleshoot. Do exactly as JMOR suggested. See tip # 13 at the link below.
You need to answer 2 questions before you do anything else:
With the bolt in the carb bowl removed and the gas on, will the fuel flow fill a pint jar in less than 2 minutes?
Next, get out your adjustable gap spark checker * , open the gap to 1/4", hook it up, turn the key on and crank the engine. Does the spark jump 1/4"? Post back with the answers.
And do not buy a new part for the tractor until you can answer this question: how do I know the part on the tractor is defective? Once you narrow the problem to spark or fuel, post back and tell us what you found (and how you found it) and you will get plenty of help to get your tractor running.
* Don't own an adjustable gap spark checker? Buy one! Not a test light! Until then, take an old plug, open the gap 1/4" ground it to the head & look for spark. Itís not the color of the spark that counts; itís the distance it jumps.