Fuel tank leak

[Grib]

I know this is off topic but relates slightly to the post title.
I've noticed a slight smell of fuel from my filler hole when the flap is closed & upon comparison with my friends Fazer I seem to be missing a small hex bolt from under the filler cap, there is the obvious fuel filling hole & then the rubber bung (with hole) by the hinge but next to that I have an empty hole where he has a nut (hex type), does anyone know what this is for and by any chance have one I could purchase?

Thanks in advance.

Yes this will be the cause of the smell of petrol, you have a hole directly in to your tank where the screw should be. You need an M4x10 cap head screw. It may be worth draining your tank too as water could have got in through the hole and be slowly rusting through the bottom of your tank. 4 of the screws around the cap do not do anything, they are just there to look nice, you could use one of those until you get a replacement.