Your first post mentioned than it may have had Duncan porting. Does your cylinder have the Paul Turner signature on the side or a part number on the bottom of the cylinder near the reed cage area? Duncan racing sometimes used a yamaha piston in some of their high rev or maximum overdrive kits.

 

Thanks for the help. No, there are no identifiying marks on the cylinder at all. It does have 85 stamped on the sleeve indicating that it came from an 85 ATC. The engine numbers indicate that it is in fact an 86 motor. I am dropping it off at a machine shop tomorrow and let them deal with getting the correct piston for it. I would prefer a cast piston as this is going to be my wife's ride. We got rid of her Banshee after she took my R for a spin. Big mistake. Don't really need to have it lightened and boost ported, just go up and down. Seems like a correct overbore stocker should do the job and still run pretty good with the cylinder work as it has the stock crank. Thanks again.

 

KNOWSALOT, You aimed me in the right direction. The 614ps if for a CR250. I am sure the rings for that piston will work as well. This post turned out to be ultra cool. Also, the more I find out about this motor, the better my deal appears to be. Hopefully I will be breaking in a fresh race motor on Saturday.