I've cleaned the gas tank, replaced the sparkplug and the carburetor but it won't start unless I remove the air filter (also clean) and spray started fluid directly into the engine. Then it runs fine (without smoking) until I release the kill switch. It won't restart without spraying the starter fluid. I thought the primer bulb might be the problem but it looks to be in good shape. Any suggestions to make this little beast crank and run like it was designed to do? Thank you for reading.