New Petter engine

I have recently aquired a stationary engine in the back a farm shed. And decided to have a go at at fixing it up a bit. Despite initially looking like I had bitten off more than I can chew, it has so far come to bits with surprising ease (touch wood!).

As I believe I have read on the top and sides it is a petter type a with 3 hp
after a weekend of soaking in white spirit, I was able to remove the sump, upturn it and squirt some fresh oil on the bearings and down the side of the piston. Once this had been done, it turned over feeling like it had reasonable compression
Im now wondering what are the main things I should check before trying to start it up?

Ill post some pictures as soon as I can but I wouldnt expect much!