Well, if the battery is spinning the motor over, then that should be fine. The next thing to try would to see if the motor is getting good fuel flow and good spark. I'm assuming you tried starting it both on and off choke. Make sure the choke is working good.
For us to tell you anything more, we really need more details on what the quad is actually doing when you try to start it. "hard to start" isn't really a great description. You need to give info like is it hard to start warm or cold? How long does it take to start? What type of motor mods do you have? Is your carb jetted for these mods? ... stuff like that. More info the better...