*motor doesn't run.
-fuel issues
1. try to start with starting fluid. if it doesnt start go to spark issue. if motor starts but dies very fast will only run if starting fluid is sprayed in carb, motor needs a carb clean/rebuild.
-spark issues.
1. motor has no spark take it to a shop, or buy a manual and follow the step by steps for your motor.
*motor runs, poorly.
1. do a spark and compression check, all cylinders should have spark and all cylinders should be within 15% of each other. example.. 110,115,112,118, bad example 110, 50, 113, 120. if everything checks ok, carbs is most likely issue and need to be cleaned/rebuilt.
2.if missing spark on one or more cylinders take it to a shop or buy a manual and follow the steps.
following these steps will allow you to trouble shoot almost everything.