Hi. I have a Yard Man Model 13AO771H055 with a B&S 19.5 hp engine (model 31N607-0726-B1). After sitting up over the winter I had trouble starting it. I jumped the starter and it ran for about 3-5 minutes when I turned it off. When I tried to start it later that day it ran for about 30 seconds and died. Now I can't get it running at all. It has good blue spark. I replaced: starter, solenoid, fuel filter, spark plug, rebuilt the (Walbro) carburetor, new battery, adjusted the valves, and replaced some old wiring for the starter, battery and solenoid. Now it cranks fast. It sounds like it's gonna start, but it won't. Any ideas? Thanks in advance.

 

Pour a couple tablespoons or so of gas into the carburetor and see if it will start and run for a second or two.

 

The gas didn't work. I'm stumped.

 

Does it have good compression? You say now it cranks fast, which makes me wonder. Was it out or low on oil when it died?

 

It had a normal level of oil before I changed it. How do I check compression?

 

Take the spark plug out and move the plug wire out of the way, put your finger over the spark plug hole and crank the engine. Does the compressed air in the cylinder blow your finger off the hole? If so, that's a good start.

 

When I cranked with my finger over the hole I felt a faint blow, but it pulled my finger in much harder. Should I check the valves?

 

If you have good spark, fuel, compression, and air all at the correct time, it should run. I am wondering about compression if you felt a "faint blow". If you felt suction, that means the engine isn't blown at least. Is the spark plug wet? Is the choke releasing when you disengage it? Does the fuel shutoff solenoid click when you turn the key on? Does the oil smell like gas?

 

I'll check the fuel solenoid and the oil. The spark plug is dry. The choke is releasing correctly.

 

The oil is good and the solenoid seems to be ok. I took the valve cover off since it was sucking but not pushing my finger, and found that the lower pushrod was out. It's not bent or damaged. So now I'm trying to figure out how to get it back in the right way.

 

Ok. I got the pushrod back in, and the bottom valve (intake) is not moving when I rotate the engine.

 

Are you sure it is in the hole in the lifter and not just stuck next to it where it goes through the hole in the block? Shine a light in there and see.

 

Yeah it's in. When I rotate the engine the pushrod moves, but not as much as the exhaust side. When I put the pushrod back in and secured everything down I checked the valve clearance and after rotating the engine the pushrod is loose again.

 

I've seen the pushrod collapses into itself, is it possible that this has happened? Usually it happens where the rod rubs against the plastic guide just below the rocker arm. It makes the metal thin until it pushes into itself. If not, there is no other reason I can think of for the valve clearance to be loose after rotating the engine unless the rocker arm stud is stripped in the head and coming out.

 

I was thinking that the crankshaft might be bad. What do you think? Everything else looks good and should run. I will try to make a video of what's going on.

 

I don't see any reason to believe the crankshaft is bad. The camshaft could be, but that doesn't fit with the valves being tight, then loose after you rotate the engine. Either you aren't adjusting them right or something is moving. The cam lobes don't change dimensions just by rotating the engine.

 

We had some bad weather for the last couple of days, so I'm taking it out of the shed today. I'll let you know what I find.