As usual, Weld offers excellent advice.
Always try the simple solutions, and use the proper test procedures before you start a difficult job which might not fix the problem.
I believe the ZS250GS employs the same AC-CDI unit as my ZS200GY-2. However, if the battery is going dead, it certainly won't have enough energy to turn the starter motor fast enough. If you don't have a digital multimeter, I suggest you get one, and test the battery voltage.
http://www.harborfreight.com/catalog...tal+multimeter
Although it isn't the greatest, the HF multimeter will diagnose a bad battery. You can frequently get of of these multimeters for free with a coupon.
__________________
Spud
"Never argue with an idiot. He will drag you down to his level, and beat you with experience."
Mark Twain
2015 Zongshen ZS250GY-3 (RX3)
2006 Zongshen ZS200GY-2 (Sierra 200)
2005 Honda XR650L
2004 Honda CRF250X
1998 Kawasaki KDX220
Mods made to my Zongshen ZS200GY-2:
http://www.chinariders.net/showthread.php?t=6894