MTD 13AE541F000 rider mower Teh 12.5 hp XL/c endura I overfilled the oil, just a little some time ago(2months ago). oil level is OK but havent changed in a while. It was hard starting about 2 weeks ago and ran surging. The surging would get less after warm-up, but returned just I was finishing mowing. Now it won't start. It will run after I put gas thru the top of the carb, for about 4-5 seconds. Ive replaced the spark plug, fuel filter. The carb bowl is filling with gas. The fuel line is clean and clear. The spark is working. After cranking, I do NOT smell gas. Ive taken the carb off and cleaned with carb/choke cleaner. Nope, no start. Inside the bowl, theres a black nipple thing, with very small holes in it that goes down in the center hole, on top of a spring. That little nipple thing had a small O-ring on the end of it. The O-ring was in really bad shape. I replaced it. After I removed the carb, the blade things were clean and moved freely. There were several small holes (where the bowl attaches) and they were clean and not obstructed. Couls the "jets" be clogged? I don't even know what a "jet" looks like or where they would be. It seems like the gas isn't getting up into the carb. There isn't a fuel pump(it's gravity fed) There isnt a oil pump or oil filter. What to do?

I have a walk type mower that no matter how much I adjust the trottle by the Handle the mower still needs for me to push it. When the machine was new, I only had to pull the trigger half way and the mower will speed up. Now I pull the trigger all the way and it does not drive on its own. I check the wheels and they are not skidding. Any idea what I need to check?