I just picked up a used WK from ebay. It came with a KA-15 esc. Is it programmable or a plug n play? I either have a problem with my battery pack (Venom 7.2v 5000 mAH) or it's the esc. I can do wheelies as long as the battery pack just came fresh off the charger. If I wait an hour or two, then I can't do any wheelies. I always disconnect the battery pack when not in use. Any thoughts?