Flywheel Spins like a Top - Is this Engine Toast?

[cjakins]

I have an older Snapper rear-engine mower with B&S engine and recently may have caused it to seize, though I'm not sure. Checked oil level, forgot to secure oil cap, tipped it up to install new blade . . . oil all over driveway. I added fresh oil, checked the level, and it showed fine. But within about 5 minutes of it running there was an awful clattering noise, then the whole thing shut down.

I then tried pulling the starter cord and it wouldn't even budge. Left it alone for a week.

Went back today, and checked the oil level first. It showed almost nothing, so I'm thinking when it showed "fine" after putting oil in, it was really a faulty reading, likely picking up oil from the side of the fill tube from when it was tipped up. So, it seems I probably did effectively run it with almost no oil in it.

I tried the cord again today, but it still wouldn't budge. So I tipped it up and tried to engage the blade/drivetrain with the engine so I could force the blade to turn. Had read where that might move a slightly seized engine. But the blade turned quite easily. Not really sure it was engaging the engine.

Upon returning the front end to the ground, I tried the pull cord once more. NOW, it pulls easier than ever, but it's because the flywheel obviously isn't attached to anything inside the engine anymore. It spins like a top. I heard nothing pop loose today like a broken piece falling loose or anything. But clearly it went from not budging to spinning like a top. So what might be the issue?

I've never had an engine apart, but I'm guessing there's a shaft of some kind connecting the flywheel/pull assembly to the engine, which turns the engine over. I suspect the awful clattering noise just before the engine died a week ago, was perhaps this shaft shearing off? And it was jammed enough not to pull at all until I tipped it up today, and perhaps unjammed?

Does any of that sound plausible? If so, is the engine shot? The mower, itself, is in good shape. Would it be worth buying a new engine for it?

 

[MRCo.]

Dunno about the jam, but the loose flywheel might be as simple as a sheered flywheel key. Part costs about $1.50.

 

[ILENGINE]

The connecting rod has siezed to the crankshaft due to lack of oil, which then broke the rod. After tipping the mower up, the broken pieces have fallen out of the way, and now you have a flywheel that is connected to the crankshaft with nothing on the inside of the engine to provide resistance. so the flywheel will spin like a top. Most likely if you would look at the engine from the head end the block will be cracked on the left side. or if electric start behind the starter.

 

[cjakins]

Thanks for the replies. I haven't taken the engine apart enough to see the damage, but it's sounding like it may be destroyed? What about a replacement engine? Would that be a wise path? The rest of the mower, though old, is in fine shape.

 

[reynoldston]

First check for a loose flywheel then. Then if not remove the engine and disassemble it to see what happen to it. Then decide new engine or repair old one. This would be my take on it.

 

[silver1]

The connecting rod has siezed to the crankshaft due to lack of oil, which then broke the rod. After tipping the mower up, the broken pieces have fallen out of the way, and now you have a flywheel that is connected to the crankshaft with nothing on the inside of the engine to provide resistance. so the flywheel will spin like a top. Most likely if you would look at the engine from the head end the block will be cracked on the left side. or if electric start behind the starter.

My Snapper had a hole in the block on the left side. You know that you hurt that engine, so check around your area and see what used Snappers are going for.
Around here they are $200 - $ 400. Also check for used B & S engines. Then you will know to replace some or all of it. The good parts can by sold to off set the cost. If you have a socket set you can remove the shroud and then the head to see the piston. It will most likely not be going up and down then the engine is turned over.