ok here we go when i got my cbr 600 f3 i noticed it had tape over the top of the battery..last week i did not think too much about it .then the bike sat for 2 days and it barley started like no power in battery.then i bump start it starts rite up so i drive it ever day to work and the bike runs great every day but if i let it sit 2 days hard to start..well today had to bump start it and bike ran like crap so i drove it to work and battery barley started bike when i pull in cluthch it revs fine but any kind of power it misses and sputters but idealing at a stop it revs great.. do i need i new battery and does the bike also run on battery and altertator. my light are dim also if that help plz help thxs...the battery has a crack on the top of it also...

 

i would get a new one just to be sure

especially if i saw any sort of cracks i just bought a new battery for mine £50

 

Your bike has all the symptoms of a battery that is going bad. I would put a meter on the battery, rev it to 4k or 5k RPM and check the voltage on the battery. If you're getting 13.5 to 14.5 vdc, then the problem is most likely with the battery. Any lower than 13.5 vdc, then you're probably looking at a Regulator / Rectifier problem. Neither of these is hard to fix. Do you have access to a meter, or do you know anyone that can test it for you ?