Arrgh! Can't get lawn tractor to start

That would be symptomatic of lower viscosity, not higher, but anyway...

That's a pretty big "only"... :)

The "clang" was probably the connecting rod end being broken off...you've hosed that baby, almost certainly...

Okay, I'll bite...

Don't try the starter fluid. Try a new engine. John

You might have sheared the soft wooddruff key on the crankshaft under the flywheel. That is supposed to happen if you hit sometime with the blade.....so you don't snap the the crank. If that is the problem,replacxe the key with the same type! If the key is seared, it throws the timing off,that is why it won't start.

I had a chance to work on a siezed up engine, last year. Please share my experience.

Remove the spark plug, and squirt a bunch (couple squirts) of two cycle "gas mix" oil into the cylinder. Then leave the spark plug out, and spin the starter for a second or two. This should re-oil the walls of the cylinder.

I didn't do this. The motor (10 HP Tecumseh on a generator) started right u p, then it threw a piston rod. I turned a $500 generator into a $75 ebay item in less than a second. I also said some bad words.

Then, too, OP should have noticed if engine spins _too_ freely_- not compressing and expanding gases. Which would make sense if rod big-end got tossed.

HTH, J

It probably wouldn't have mattered a whit if you had...the seizure more than likely overstressed the connecting rod anyway and it was inevitable.

As noted before, I'm wagering it was the end falling off after the "clang" that freed it up for OP...

Ah, I do feel better. I'd spent most of a year berating myself for not oiling the cylinder. But, if there was a different problem, maybe I couldn't have saved it, in any case. Thank you.