Yes, I understand that. Everything has been changed. I pulled the head thinking that the valve seat might be been compromised. Cylinder looked good, no scores on piston wall and sealed from what I can see, cylinder looked better than most I have seen. I installed a new head gasket, reinstalled the head, pushrods and rockers, retorqued as per manufactures specs. Pulled carb and cleaned everything. The float seat was dirty, and the fuel solenoid was not working properly. Reinstalled everything and now get a large flame out of the carb. I also checked both valve seats while head was out and both valves were seated and sealed. It appears that the timing is off, but I am not sure how this is possible, since from what I see from the service manual the lifters are driven off of gears. Even if engine was rotated backwords it should not cause a problem.

Those are the classic symptoms of a clogged vent hole in the gas tank filler cap. These vents can become clogged with the fine airborne dust that is carried into the hole during operation. Over time, this dust can pick up moisture and will bond together, forming an almost air tight plug. Sometimes a small wasp or insect discovers the hole and sees it as the ideal site to deposit a clutch of its eggs. Probe into the vent hole of the cap with a piece of stiff wire (paper clip) and then tab the cap against a hard surface and see what comes out. If you have a source of compressed air you can gently and carefully blow into the vent hole (not while it is on the tank!) to clear out debris after probing with the wire. Checking to see if it is due to a clogged cap vent can be done by simply removing the cap for a moment (breaking the vacuum that has developed) when the tractor begins to falter. If loosening the cap restores the good running of the engine you have located the culprit.

Thank you, Mike, for that information. Yes, I also feel his diagnostic skills are lacking. He did replace the carbureter. Since he did that, now the mower won't start at all. He was trying to put the new one in and the plastic piece was not allowing the metal insert to stay in place right. I went in the house for a few minutes, and when I returned he told me he "found another carbureter to use instead since that piece seemed faulty". Now I'm wondering if he might have used it anyway, and maybe that's why the mower won't start now. The manual says the carbureter may be one reason a mower won't start. I have never heard of a "magneto grounding wire" before. Can you direct me to where that is located? Does anyone know if the fuel filter is supposed to fill up all the way with gas, or just be partially filled, when turning on the engine? See pic. Thank you again! Cathy

I agree with tomplum. I am a sears service tech and I think your valves need adjusting. I have been on so many calls where the mower is doing what you say and it is the valves adjustment. If your model number under the seat starts with 247.****** I am sure your valves need adjusting and probably your rocker arm stud tightened. Put loctite on the stud if it is loose.