I have a 2002 Rancher 350 with only 250 miles. (don't drive it much). Has been 3-4 weeks since I started it. Battery is good, but just keeps turning over and then eventually backfires.

 

check the spark

 

I assume you can just disconnect the wire and see if it arcs to the plug?

 

that or take the plug out with the wire connected to it and turn the engine over
that'l be more accurate

 

Thanks. Looking ahead, if it has spark I guess the next step might be replace the plug and maybe the gas?

 

The spark plug is fouled. Most likely from setting so long the fuel in the float bowl lost its volatility. When you went to start it the bowl full of fuel was bad and fouled the plug before good fuel was replentished into the carb.
If you will not be useing the quag for long periods of time, I suggest dumping some Sea Foam fuel treatment in the tank, let it run for about 15 minutes and turn the fuel valve off on the tank. Eather let the unit run out of gas with the fuel valve off, or drain the carb. The fuel drain is on the bottom side of the float bowl on the carb. The screw does not need to be removed, only turned open a few turns to drain the carb of fuel.
Once the carb is drained I like to pump the primer button and turn the engine over with the starter (fuel valve off, choke pulled) to rid unstable fuel from those passage within the carb. This process makes for a clean start up days down the road once the fuel valve is turned back on before starting

Hope this helps

----- Gimp -----

 

If it doesn't get ridden much, good chance the carb is all gummed up! Idle jets are particularly vulnerable.....

It backfires because it is lean, and not getting enough fuel due to the clogged jet.