Giddy Gadge,it's the tap on the petrol tank, it is all plastic, has a red lever that turns from off to on, it's is leaking from that red lever. Things I learnt today- some rattle can paints, don't like petrol, a good catcher is worth its weight in gold (not that I want to pay that much for it), mesh catchers leave you covered in dust and grass, the heat from these old girls is very extreme, great for winter though, a freight train with no exhaust is quieter than a 125 cc motor with a box exhaust and last of all, I'm not as young as I was when I last used one of these mowers, could you imagine using one of these with out ear muffs now.
Cheers
Kirky2