Petter A1 or is it A5 (starting issues and no serial no)

Hi I have just brought a Petter A1 or is it A5 the magneot is mounted inline of the cam at the starting handle end and has a cast timing cover , so what model is it, and its engine plate is missing ,so where can I fine the serial number stamped, there is a plate on the top that tells you how to start and run and stop the engine , its been sitting for a while, used be used for generating set before national grid arrived, so I checked it over oil is clean loads of compression does have spark not great, I checked the carburettor and cleaned out using carb cleaner and compressed air , when I go to start it I get and cough and that's it but I am winding and winding it over and over on the starting handle and get another cough, if I used the generator to start it( has 12volt start windings) it does the same and eventually it starts and runs quite well and I can get a nice tick over ok too but when I open the governor it splutters and then picks up speed. ive seen youtube clips and these engines start at the first or second swing.
So what can be wrong, what plug should be fitted what is the best settings on the carb, (its a solex 26fv) I think does anyone have any ideas what wrong, john

Sounds like a Petter A (not A1) or AS type if the magneto is on the front of the engine.

Magneto is on the outer side of the engine, it sits next to the starting handle if that helps