We got a Honda mower, used, but in good shape. However, last summer the wrong fuel was mistakenly used. It conked out. We drained it. Added the correct fuel. It eventually starts, while it spits and sputters (with lots of smoke) and after about one turn in the yard it stops and is very difficult to restart. Repeating the aforementioned problem. Is this mower ready for burial? Or is there something else we can do?
Small Engine Tune-Up
Change the spark plug. You should be able to see the model number printed on the plug, and/or stamped on the engine/Heads/Jugs and/or on a sticker. Most Home stores sell Spark Plugs for lawnmowers. If you can't find one there, try an automotive parts store, a Tractor Supply, or the Internet.
Clean the Carburetor
Remove the carburetor and clean it out with carb cleaner.
Visually inspect the fuel hose. Feel it between your fingers for dry-rot, or any damage. It's best to just replace it, given the cost. Bring the hose with you into a Retail Store, or order a length online. You can use a micrometer to check the inner and outer diameter of the hose and the fitting(s) on the Petcock, tank, carb etc. The old hose may have swelled, so if you're over by a tiny fraction, you should likely size down.
Again a Home Store, Tractor Supply, Or Internet should be able to get what you need.
Try running some SeaFoam, or another Engine Treatment, in the fuel. Here's a link to SeaFoam's Article on Lawn Equipment Tips
PartsTree.com: OEM Replacement Parts for Mowers, Trimmers, etc. Has some great exploded parts diagrams, too!
SearsPartsDirect.com: in the event that it's a Sears Mower Deck, Engine, or a sister product. PartsTree is great for that information.
HondaLawnParts.com: As the URL suggests, OEM parts for Honda Lawn Equipment.
I've gotten numerous lawn mowers going that people have thrown out simply giving them a good tune up!
Hope this helps.
Using 2-stroke gas or diesel in a lawnmower will foul the spark plugs, so some smoking and sputtering is to be expected. Probably there was still some residual oil/diesel left in the fuel line after draining. Take out the spark plug, clean it and try again. The lawnmower should run fine after a short while.
I was once faced with this problem. Kerosine was used to top off the fuel tank. Draining the fuel tank, and installing fresh gasoline helped, but the engine would not run. It would sput and sometimes fire. I took off the recoil started, and mounted a socket on a drill, and cranked the mower for a couple of minutes, with the plug wire pulled. Then I pulled the plug and cleaned the kerosine off it, and replaced, connected the wire and voila, it worked. A little extra smoke for about 20 seconds.
Basically the engine needed extended cranking to clear out the kerosine in the carburator.
In the OP example, it would start with cleaner, because it was burning cleaner. The fuel he was burning was probably not volatile enough, hence the restart process.
If one is not comfortable with a socket to the crankshaft, on a drill, then the hand starter can be pulled repeatedly.