Sun joe mower: how to fix blade

We need to divide the problem in half. In the case of an engine we need to decide if it's not starting because of gas or spark. Too test the engine for spark your going to need an extra set of hands or some electrical tools. If you have help you can have some one hold the spark plug wire close to the spark plug while you pull the string. If electricity is getting to the spark plug you will see a spark jump from the wire too the sparkplug. IF you see a spark we can now trouble shoot the fuel.

The easiest way to check the fuel would be to buy a can of ether, that is what the guy in the video sprayed into the engine. If it runs for a couple seconds (or even acts like its about to start) then we know the problem is with the carburetor or fuel system in general.

If you complete these next steps please come back and +1 my answer(so I get a notification) and I will continue to assist you in trouble shooting. Regardless if it's spark on fuel the trouble shooting only get more and more complex from here. I would replace the spark plug and if that doesn't work I would look at calling Home Depot, they might even pick the lawn mover up for you. They are good people.

How to check for spark video https://www.youtube.com/watch?v=mUOmsGiirTU

Once you fix the carburetor leak, try to start it. Common problems are:

• air filter dirty- remove the air filter element and replace it or clean it thoroughly.
• carburetor jets plugged- you said you "cleaned" the carb, but did you completely disassemble and make sure the jets were free of gummy varnish and residue?
• old fuel- you state that fuel is "1-6 months old", 6 months is too old. You should drain all the fuel and replace with fresh.

Gasoline in most areas now contains a percentage of ethanol (ethyl alcohol) which is bad for older fuel lines and other components. You do not say how old your mower is, but you should inspect and replace any fuel lines that feel soft or gummy. Also, drain and clean your fuel tank and lines, flush with fresh fuel. Ethanol tends to absorb water from the air which will settle at the bottom of your fuel tank over time. You should try to use only fresh fuel (no older than 3 months) in your mower.