When fuel sits for a long time, it deteriorates and can gum up your carburetor with sticky varnish deposits, causing tiny passageways to clog. When this happens, your engine can’t get the appropriate air/fuel mixture, resulting in hard starts, rough idle or no start at all.

If your engine starts, but runs rough, or if it’s starting hard, you can try cleaning your carburetor by adding Sea Foam Motor Treatment to your fuel and running Sea Foam Spray through your intake as shown in this video.

If your mower is not starting, you may have to remove your carburetor, clean it and reinstall it, or replace it entirely. This is a simple job for a small engine technician, but is also a DIY project if you have a little patience and a few tools. Though they all operate the same, carburetors differ by manufacturer, so you’ll want to consult a service manual for your model for proper disassembly.

Most importantly, you’ll want to make sure that the float bowl and primary jet are clean. You can do this with Sea Foam Spray and a soft wire brush.