[Masteryota]

Ok, lets start with the simplest thing. For the start button, you do know you have to have the brake pedal depressed for it to turn over? It's a factory safety thing. You may have a failed start switch, but check this first.

Second, you mentioned a manual. Assuming you have a wiring diagram from a/the manual as well. This will make sorting the electrical much easier. In simplest terms, I try to match the wire color code at the plug with the diagram when rewiring vehicles. Most times if you or someone else has to diag something, they won't need to look further than right at the plug to match color codes.

Third, do you know what happened to the previous engine? This could play into why it runs poorly, or may not mean anything at all. Make sure you have adequate fuel flow, and there isn't any trash in the tank or the inline filter. Even though the carb looks new, take it apart and make sure the pilot jet is not clogged. The hole is very small, and easily blocked with the smallest particle of junk. Then look at the plug and coil and make sure you have adequate spark, nice thick blue spark is needed. Report back anything you find, or more questions. Start with the wiring, then check for fuel and spark.