I have a 1990 moto 4.
Can I charge the battery while it is still connected to the bike?

 

Sure thing. Just remember it is always better to trickle charge a battery at 2 amps to a full charge rather than a rapid high amp charge. Also, if your atv sits alot, think about a battery tender. They have a pigtail you leave connected to the battery and plug it in while not in use. It keeps your battery fresh, which is always a good thing since they are so expensive!