Briggs Stratton Seized?

If it's the first case, it was fine and now is stuck, it's most likely something mechanical. From a nut dropped down by a squirrel blocking a valve or piston to something in the fan shroud. Moisture lockup is possible as well, but not as likely. Unless you've parked it in the rain with the air filter off. These are all pretty easy fixes with minimal costs.

If it's the latter, it was running badly and brought home, it's much more likely oil starvation. Could also be overheating. Remarkable how well mice block out the air passages with fluff. The repair cost is normally quite high, making engine replacement more worthwhile. If it's an overheated seizure, you might get by with just a piston and ring replacement.

Remove the cover over the flywheel.

The starter gear may be jammed in the ring gear. You should be able to see it, and if this is the problem, rotate the engine backwards a little to see if it frees, If not, you may have to remove the starter.

OR, it could be the ignition coils that are right next to the flywheel. V-twin has 2. If it sits long enough, the flywheel can rust enough that the coils get stuck to it. They"re only a business card thickness away from it. Doesn"t take much to get them loose, but the starter isn"t strong enough to do the job. Remove the coils, sand off the rust, and reset the coils in place. a business card between the coil legs and the flywheel magnets should work.

Also, in the late summer and fall, mice like to move in to small engines and make a nest near the flywheel and coils also. They can stuff enough stuff in there to jam things up, especially if any of the nest material go into the starter gear and ring gear on the flywheel.

Walt