Bad gasoline and bad oil are two common causes of failure to start. If the ATV has sat unused all winter, gasoline absorbs moisture and goes bad. You can smell bad gasoline because it has a varnish-like smell, instead of a normal gasoline smell. Also, oil thickens over time. The solution is to change the gasoline in the tank. Change the oil as well, and this eliminates two possible problems.
A bad spark plug is another common reason why your Kazuma won't start. Spark plugs go bad over time, and if's been a while since you changed them, go ahead and do so. Signs of a bad plug are heavy carbon deposits or oil deposits on it. Also, the ceramic insulator may be cracked, which will prevent electrical flow.
If the ATV has sat outside for a long period, odds are good that the weather destroyed some components by corrosion. Severe moisture and rain will attack sensitive electrical parts such as the coil or magneto. The diagnosis of this problem is difficult, requiring professional expertise. This is because this type of damage affects many parts. Kazuma has a fully stocked parts department, so finding replacement parts is not difficult.
The battery may have gone dead. This is especially true if the ATV has been inactive for awhile. The solution to this problem is to remove the battery, and put it on a battery charger overnight. If you are not sure how to remove and replace a battery, a qualified ATV technician can do this for you.