No start is caused by one or two issues. Gas or spark.
first check for spark. Get a spare spark plug and remove a spark plug wire from one of the plugs in the engine and put it on the wire that you removed. Then hold the bottom electrode of the spark plug to the engine for ground and have someone crank the engine over. Is it getting spark?
If yes, then make sure that you are getting fuel. Cycle the carb linkage and look down the carb for a squirt of gas. You should get a squirt when you stroke the linkage. Or get a jar and pour a little gas down the carb while holding the throttle open. Then crank it over.
If you are getting gas and spark, then it's just a matter of finding the right spot to set the distributor. For a fresh start, put the engine at TDC, and remove the distributor cap. Look where the rotor is pointing to, and then put the cap on and get the #1 spark plug terminal to line up with the rotor (and maybe a few degrees advanced). then crank the engine over, and it should start, then set the timing with a timing light when it's running.
