2003 Kawasaki KLF250 Service Manual., Page 256Get this manual
16-14 ELECTRICAL SYSTEM Battery
Ordinary Charging
Remove the battery (see Battery Removal)WARNING
Keep the battery away from sparks and open flames during charging, since the battery gives off an explosive gas mixture of hydrogen and oxygenWhen using battery charger, connect the battery to the charger before turning on the chargerThis procedure prevents sparks at the battery terminals which could ignite any battery gases