Is this a twinshock SRX600 ?. If so the charging and ignition systems are seperate so your poor starting is unlikley to be due to a poor battery. That said Ive spoken to several people who are adamant it does make a difference.
A weak bubbling noise from the battery doesnt sound good, if you disconnect the red wire from battery when the ignition is turned on do you get a spark from the red wire to the battery wire ? These a fuse inline with the battery does that need resetting ?