I was recently given two weedeater mowers, one a 5 hp high wheel model. The other a 3 1/2 hp mower. After priming, both will start briefly and then stop. Both have new plugs and fuel. I do not have a manual for either. And I do not understand the throttle system or lack there of a throttle.so I would appreciate any information you could give me in any way you can tell me how the throttle systems are supposed to work. Thank you very much