So I have 110cc go kart that I had gotten recently and sometimes it has trouble turning over the engine during the compression strike, it's has a brand new battery which is a ST5L-BS, it works fine until it hits that compression stroke and drags really bad and doesn't want to turn the engine over, so I am thinking maybe the battery is to small?? What size battery would I need or do I have the correct one ??

 

With those tiny batteries, going one size too small makes a big difference. Answer, measure battery box (height as well) and get the biggest 12v that will fit in. Make sure the pos and neg posts are right for your wires, as most battery sizes can be bought with the terminals either way. However, other things can cause a sluggish starter, battery connections on the thick wires being corroded or not tight, including earths. A slightly slipping starter clutch can cause problems too.