I am running a 13T/46T sprocket combination. Riding the bike hard on the interstate highways, I
once got a low of about 56 mpg. However, I am usually gentle on the throttle, and usually get 66-73 mpg.
I agree with George; I think you should check your valve lash.
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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