Hi, Anonymous if your bike has been sitting idle for months or years and you did not do any pre-storage maintenance I feel your pain it will probably have a dead battery and not want to start or if it starts it will idle and run poorly, here are the following steps necessary to complete in order to get your bike back to an acceptable running condition.
1. If your battery was 2-3 years old when you last had the bike running you should replace it.
2. If you believe your battery might still be serviceable remove it from the bike and put it on a 1 or 2 amp trickle charger for 24 hours. If it is the old lead acid type with visible cells and acid levels fill each cell to the top line with distilled water and replace the caps, run the vent tube into a plastic or styrofoam cup, any cells that are cloudy/milky replace the battery.
3. After charging remove the leads and let the battery sit for a couple of hours then check the battery voltage with a volt meter, you should have 12.5 volts or better, any readings in the 11 volt range you need to do a proper load test on the battery and replace as necessary, any readings in the 10 volt range you have a dead cell and replace the battery.
4. Drain and flush fuel tank, google " how to clean a motorcycle gas tank" find a couple forums to view the different options available.
5. Remove your air cleaner and clean and re-oil per Mfg. specifications.
6. Remove the carburetor, disassemble and decontaminate with a carb dip or if you have EFI remove injectors and clean with carb spray and compressed air
7. Remove fuel valve and filter disassemble and clean as necessary, remove fuel lines and replace with new ones.
8. Replace spark plug with a new one and check for spark.
For more information about your issue and valuable "FREE" downloads that you will need please click on the links below. Good luck and have a nice day.
250 sxf wont idle 250 350 450 505 SX XC 4 Strokes
2012 KTM Fuel Injection Filter Discussion Enduro360 com