I have a Garden Pro lawn mower with a Robin Subaru EH-18 engine the classic steel one. My problem is to start it I have to manually work the choke, there is no cable running to it. If I release the choke and rev the engine it quits running. I was not able to see the spark, when I checked the spark plug. Not sure if I am looking at a carburetor or electrical issue or a little of both. Any ideas?