99 GS500.  Pulled battery (5+ years old) out for the winter.  Periodically trickle charged it.  Battery tested within range (~12.5V) when on bike and off.  Hook up to bike...nothing.  No power at all.  I do get a rotten egg smell and a battery getting very hot.  I'm replacing that battery today.  Bike was fine went put away last October.  Is there anything else I should consider?  thanks

Sounds like you have a short somewhere.

Google "Motorcycle battery testing".  Any good procedure will have a step to check and see if there is a short.