I have a Toro 20065 mower bought in 2008 that won't start. Late last year (I'm in FL so we mow all year long) the mower started to surge on start but would soon level out, and then the primer bulb melted off. The gas was about 5 months old - probably older than I should have been using, but I've always bought 5 gal at a time and just kept using it - the new mower goes through less gas since I only have to fill half the tank to get through the whole yard. I replaced the primer bulb and switched to using 2 gal gas tanks, and wondered whether any other parts inside had been damaged.
Last Saturday the mower kept almost stalling out. The gas was only about 2 months old but I decided to go get fresh gas. I also stopped into Home Depot where they told me to use Mechanic In A Bottle in the gas. The instructions said to run the mower for 10 minutes but when I went to do it the next day, the mower wouldn't run for longer than 30 seconds at a time. I kept starting it back up again to get the cleaner into the engine as much as possible. The next day the mower would not start at all.
First I checked the fuel line. The fuel was definitely running to the carb (and also taught me that the tank has no fuel cut-off valve). I had some difficulty removing the carburetor and may have accidentally bent the governor wires above it a little. I was expecting the bowl to be all gummed up but it was quite clean, though the gasket was getting worn out. I cleaned it anyway and sprayed the carb down with cleaner, then put everything back together. It would still not start - if anything it sounded 'more dead' than it had previously. I also changed the spark plug, which made no difference. Shooting starter fluid into the spark plug chamber would let the engine start for one second before it would instantly die again.
I bought a carburetor overhaul kit and replaced the gaskets and the float valve pin gasket/seat, I shot carb cleaner through the nozzles to clean them out. I then put it back together and learned how fast it leaks when you forget to put the float valve pin in.
After putting everything back together properly this time, the engine was still the same - would not even try to start.
One thing I have yet to try is from a comment in a thread I found here that mentioned that the air filter / primer assembly may be warped, but I would think that even if there was a problem with it the engine would at least 'sort of' start up instead of being completely unresponsive. Is there any way to test if this is the problem before I go out and buy another one - the parts store is far away enough that I'd prefer to have at least some clue of what's really wrong with the mower. Someone else mentioned it might be the magneto. At a minimum $90 charge to work on the mower I may as well buy a used or even a cheap new mower and give the broken one to them than to actually pay for repairs - it needs a new starter cord too.
Thanks for any help you can give me.