Many of the motocross racing bikes have a piston with a single compression ring, which facilitates operating at high rpms. However, most non-racing engines have pistons with two compression rings, which reduces contamination of the engine oil from combustion gasses, and increases the life of the piston rings. The Zongshen RX3 has a piston with two compression rings.
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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