I buy my parts on ebay. Last time they came from South Carolina.
If I was replacing the piston and cylinder I woould step it up to a 170. I think the number of bolts on the valve cover gives a hint to the type. I have never had one open. Just worked on the CVT.
Here is a link to the red springs.
http://www.ebay.com/itm/SCOOTER-GY6-...a5ebfc&vxp=mtr
There is also yellow. 1500 rpm.
Slider weights. These are 10g.
http://www.ebay.com/itm/10G-GY6-150C...2d8387&vxp=mtr