10W works well with these bikes, the heavier the oil, the greater the restriction as is passes through the oil ways. Lighter fork oil passes through the oil ways more quickly leading to the front shocks compressing faster and more quickly.
10W and a good rear shock gives a nice tight ride...
The mis-fuelling metal pipes pass through the fuel in the tank. If you have fuel continually dripping/leaking from the rubber hose then the metal mis-fuelling pipes in the tank are corroded or the where they exit at the bottom of the tank has corroded.
Carl