Yardman won't start

Have an MTD Yardman 42" deck riding mower powered by a 17.5 B&S engine. Mower often would not start last year. Went through a partial stroke and then hung up. Had a repair man look at it and he got it started, but wasn't sure what the problem had been. This year it started out fine but old problem returned. I replaced the starter switch and problem went away for a few weeks, but now it is back. Engine usually hangs up at about the point of max compression. Always at the same point. I can manually rotate through a full cycle, and I tried using a jump starter which gave me a full rotation, but then hung up at the same place. I also tried holding the key in the start position and got the engine to slowly rotate through one stroke. I also heard an electrical sizzling sound when I did it. Can someone help me? thanks.

 

Your valves need adjusting. Hopefully you haven't burned up the starter by now. The valves are too loose, disabling the compression release.

 

Sure sounds like the solution. In researching the best way to adjust the valves I find clearance recommendations ranging from .002 to .006. Quite a difference. This machine is about 5 years old and probably has 200 hours on it. It has never had a valve adjustment. What clearance do you recommend?

 

.005" on both valves should put you back in action. Make sure you set the engine 1/4" past TDC just after the compression stroke (on the power stroke).

 

First the good news. I reset the clearances and the motor started. This meant I hadn't burned out the starter and the valve gap was my problem, as you said. There are still two problems..I have to crank forever to get the engine to fire, and when I shut down there is a backfire (I had this before). Is it possible I set the gap too tight and that is causing thelong start?

Thanks.

 

It's possible. They should not be set so tight that the rocker arm doesn't have any play.