Richard wrote:
Folks, I have an older Craftsman lawn mower that I can't get to start.
I do get a good spark, so I'm assuming that it means a clogged
carburetor. Is there anything that I can pour into the tank and allow
to sit there that might help dissolve any old varnish? Thanks in
advance for your suggestions!

More than likely varnish has formed over the fuel pickup screen.
Remove the carb and blow everything out with aerosol carb cleaner.