Problem: Rev's suddently jumping down

Hey...my battery is dead again. I jump start it and get it running for a bit.

Problem is that when i rev it up to about 4-5k, then let it come down, itll jump for about 4k to 2-3k in an instant! I feel the exhuaust pressure and that stops during this drop too. I didtn have time to recharge the battery all the way up today.

Is that drop related to the battery?

Btw..how long will it take for it to recharge?

Thanks.

Its a 2001 and was flawless just last week, so I doubt its dirty carbs, right? Also, the throttle goes down smoothly, its just the revs that dont.

Any other ideas?