The bike is a 1998/99 Honda CBR 600F. The drain tube seems to be corroded inside the fuel tank, based upon 2 symptoms:

• Filling the tank more than 3/4 full causes petrol to drain from the drain tube
• Water which collects around the fuel cap (eg, during rain) dribbles into the tank, rather than escaping down the drain tube

I've been advised that the correct fix is to replace the entire fuel tank.

Whilst searching for a fuel tank to buy, I noticed that individual drain tubes and breather tubes are available, and I wondered:

Maybe these tubes are replaceable without replacing the entire tank?

Trouble is, as far as I can tell, these tubes are inside the fuel tank, and therefore impossible to get to. Or are they?

Example: see parts 15 & 16 in this schematic