200s/x top end
for all practical purposes, the top ends are the same on both the 200s and the 200x. The primary difference is the 200s has a compression relief valve (right side of the rocker box on the exhaust valve), and the cam lobe lift/duration is a little different. I just finished building a 200x with a 185s head and rocker box (same as 200s). I'm using the stock 200x cam, a dg header, 10:1 piston (1x oversize), and uni filter. I currently have a .110 main jet in the carb and it seems to idle just fine. My throttle cable is toast, and I have to put about 10 hours of easy (1/2 throttle or less, and no throttle bursts) riding on it before i can tell you exactly how that jet's going to work out. I'll let you know something after i get 2 or 3 good hours on it, and read the plug.
I'm not certain about the xr200r carb, but i think it's the same as the stock 200x carb (24mm I think).
Darrell
83 185s *Now belongs to my nephew*
83/84 200x
85 Tri-Z
85 350X
85 Tri-Z Parts Donor
88 Yamaha Moto-4