My Z425 won't run. I cleaned and put a new kit in the carburetor, new spark plugs, changed the oil & filter, new fuel filter, new fuel pump, new air filter, new starter ( which is why started this project) and all it will do is sometimes start but won't keep running. When it runs it runs sluggish then dies. It ran before I changed the starter. I pulled the flywheel and reinstalled it to get to the starter. Any ideas of what to do next?