420 Motor Lockup: What'd I do?

[Whitty]

Had trouble starting my 420 during the winter so I gave up. (I think I'd water in the fuel filter.) This Spring I started it & it ran about 10 - 20secs when I heard a loud *CLANK* that almost rang like a bell. The engine stopped dead - no spindown. Applying current to the starter elicits a grunt & the fan blade jiggles once, but no cranking.

Very worried! So far I've removed the valve cover & noted that the valves stems seem in place & there's a little valve lash; so I'm thinking that's OK.

I'm looking for suggestions. I'm not an HD equipment mechanic but do most of my own car repairs. Thanx in advance.

[Lavoy]

I locked one up like that years ago, turned out to be the hyd pump.
Lavoy

[Little John]

Whitty, I pulled a sleeve on my 440, years (35) ago. It was on a warm start up however, and did not get to run at all. Clunked to a stop and did not ring at all as I recall. Re-sleeved it with a 'larger at top' sleeve. In those days it was cheaper than the pump I had to replace a little later !!
Good Luck, Mora