Gas leak i just bought a xj 650 yamaha maxim we put gas in it, and its been in my back yard for about a week. everything has been cool until about 4 days ago,when i noticed a pretty sevear gas leak .the bike is not running because it needs a new batt.

So you have a hole in your tank somewhere. or leaky fuel **** gasket. firstly you need to find the leak. or is your gas just flowing right thru your carbs and out the overflow? shut off fuel to eliminate carbs. if it stops leaking then its probably gummed up carb floats. use Berrymans B12 fuel additive this will work into the carb and hopefully break down the gum. or strip and clean them by hand with a good spray carb cleaner. or remove air cleaner and spray directly into carb and let sit for a few days.
if it's a gas tank leak then you will have to get it lined, (liquid sealer) so long as the hole is not too big. if it is then drain and dry the tank, get it welded professionally or patch it with a filler or fiberglass and then get it sealed, i used my local radiator repair shop to het mine done.