I really feel for the first time like I`m getting somewhere now! I have finished the valve except the springs – need to sort those out as currently they are just 2 random springs I found just to hold it all together.
And I managed to get an M10 tap (thanks again Rodget!) with a fine pitch for the spark plug and so far, assembled it looks like this:
So now I need to decide where to go next! I`m going to go with a vapour carb but I don`t know if I should go with the ignition system next – there are no instructions with this one from China so I haven`t a clue what to do with it!! What power supply do I need?