Seized? Lister D

I have two D's

I have struggled to get one going but a carburettor strip and reset led to it running well on Sunday.

I ran it for a few minutes and shut it down normally.

When I came to restart it later on it appears to have locked.

There is a minute amount of play only on the flywheel, other than that it is solid.

I cannot understand how this can be.

Any ideas welcome, please?

(Removing the plug does not help one bit.

Ken

You could check to see if the magneto is seized. If it is , the chain would stop the engine from turning but give you a little bit of play on the flywheel. I had this problem with an early shaft driven D.