Ok, got an extra lawnmower late last year, a self-propelled one since my son is starting to help out. It’s one of those that you have to add some oil to the gas. I only added gas to it once last year before the end of mowing season. This year I pull it out and top it off and start to mow. Get through half the front yard and it shuts down on me. Now the string won’t even budge for me. Then the idiot light bulb goes on and I realize I didn’t add the oil to the gas when I filled it up. I am not mechanically inclined at all. So what did I do and how can I fix it?

Was this a new mower? I only ask because two cycle lawnmowers aren't as common as they used to be.
The bad news is, a stuck engine is usually terminal. You can try removing the spark plug, pouring a couple tablespoons of motor oil,(automatic trans fluid works best),into the engine, LEAVE THE PLUG WIRE DISCONNECTED!!, and reach under and turn the blade to try and free up the engine. Be sure and clamp the operator presence bail against the handle first.
You might break it loose, but the damage, in the form of scored cylinder walls/and or rod journals, is done.

If it does come free, mix some gas/oil, heavy on the oil, and try your luck. It might mow for years, or it might mow for minutes.

It all depends!! Been waiting for my chance to say that...

Living up to the username! Thanks sparkplug! I found a couple tips online too, but wanted to see if anyone has had this happen themselves and see what they did to fix it...if it could be fixed. I'll tinker with it.

My son really wants me to get it fixed.

Put the trans fluid in the cylinder and let it soak for at least 24hrs. The lack of oil cause friction which in turn causes heat metal expands under heat. So with motor being cool and the ATF soaking in through the seals there is a good chance you can get it to run again.

Even if you get it running again it is toast after that much usage on straight gas.

I agree with Dwight you might get it freed up and it might last a few hrs but I think it is done. I had a ski doo seaze up once and got it free but it lasted about 4 hrs. You might be better off just taking it apart and replace the piston and pot before it sends pieces in the crank and wrecks more stuff( like I did)

If you do take it apart, you might need to hone the cylinder a bit........

Save yourself a headache and buy another one if you financially able. If you have seized an engine do to lack of oil. Its going to have major problems if not right away it will later. You would need to an engine overhaul to fix it.

I think there are two things that MIGHT work in Omaha's favor.

If I understand him correctly, he added gas to last year's fuel mix already in the tank, which should've had oil mixed in it. The ratio would obviously be off, but some lubrication is better than none.

It's a two cycle, which typically use needle bearings in the rod, and possibly ball bearings on the mains. (depending on the brand). Those components don't require much oil at all.

So we're left with the piston and cylinder, both made from aluminum. You can't run aluminum against aluminum without galling, so typically you install a cylinder liner, made from cast iron, or you apply a layer of industrial chrome plating to one component.

What I usually see in this situation, is a piston with vertical streaks of smeared aluminum, which binds the rings in their groove, preventing them from expanding tightly against the cylinder wall.

IF, the cylinder has a steel or iron liner, you may be able to hone it and remove the aluminum transferred there by the piston. The piston and rings are probably toast. If it was a plated engine, The whole thing is probably toast.

I have seen some run for years after seizing, and others run only a few minutes.

I apply a rule of two in this situation:

"If it's over TWO years old, and you paid less than TWO hundred dollars for it, think carefully before spending major money on it"

Best thing to do is.. Is find a local mower repair place and see if they'll give you some money for it on trade in since it's fairly new..

sprkplug:

I've melted many a piston in my time. Snowmobiles, 2 stroke, adding oil to gas. Temp changes, loads, etc. Not pretty at all. I think only once did I actually make a hole in the top of the piston, but I sure did crater a lot of them! I went so far as to install pryometers in each cylinder. Even then I still cratered one more piston. Each and every time I was able to hone out the cylinder, and only once (when I holed the piston) did I have to change rod and crank bearings.

I think the only way to tell for sure is to take the motor apart and see how bad it looks.

Omaha, can you take out the plug and show us what it looks like?

My brother toasted an almost brand new chainsaw that way. Put gas in from the wrong can. New piston, rings and cylinder were in order. Now all of the cans are properly marked.

I melted a piston once. (actually several at once) I put a 440 in my 72 Cuda out of a 69 Imperial. My brilliant idea of adding a pint of Cox airplane fuel to the tank yielded in some short lived fun. Sure did improve performance, but the old pistons couldn't handle the heat. Back then, engine and transmission changes were quite routine

And tuneups were every 3,000 miles, weren't they? There was a thing called points back then.... Mom & Dad bought a new Imperial Crown in '67 with the 440 4 bbl in it. I remember standing on the floor in the back, watching the speedo sweep to the right of 120 mph when Dad was playing with a Mustang. The Mustang was quicker away from the light, but Dad passed him on further down the road - IIRC 2:73:1 gears?

Yep! As a kid I had a pile of those old .049 cox engines, all with melted pistons. That nitromethane burns hot!!

Chainsaws are far and away the most common engine I see to stick a piston. Sometimes it's because of wrong fuel, but I have seen it caused by some backyard "supertuner" leaning out the mixture screws.

They always say the same thing: "I don't understand, it was running better than ever, then it just quit"

Let's see. A lean fuel mixture burns hotter. Strike one.
A lean fuel mixture contains less lubricating oil. Strike two.
A lean fuel mixture causes the engine to turn more rpm. Strike three.

And a chainsaw, due to weight concerns, doesn't usually have a sleeved cylinder. They run a plated piston, so it's new cylinder, piston and rings.

It needs to be an expensive saw, or you really gotta' love it to undertake repairs of that magnitude. $$$$$$

I'll tell you about an unintended consequence of your stupid stunt. You've made me realize that I'm not the only one who does stuff like that.

Thanks for all your help guys. And happy to see I'm not the only one who has done this. I wasn't able to tear into it this weekend, but will jot down all the advice and get at it soon. See if I can save it.