Hi, i just bought 2. Electric bike kits off a mate who used them a few times each, they are the cheap ebay 1,500 watt front wheel gearless brushless kits. Im running on 4. Regular 12v.7ah lead acids. I have installed one kit atm, and when i took off it was all good bit when i reach about 20kph the whold thing shakes like crazy, the wheel looks straight when spinning and when i lift wheel from ground it spins fine, but when i ride the thing vibrates forward n back like mad!!! Please help?