Jim,
Are both the X and the R the same type of radiator cap?
Just wondering if the X cap allows return whereas R may not as never had the overflow tank.
Yes they both use the same cap , the same overflow outlet , which is where the tank hose is connected , one flows to the ground and one goes to the tank to be recovered when it starts to cool down , and the tank has its own overflow should the thing overheat to the point where it filled the tank , it has somewhere to drain out ( you start off with the tank half full , so it can accept then suck back coolant), so pretty much its the same closed system for both bikes , with the exception that at the factory because the R is not setup to be trail ridden they omit the overflow tank , where the trail ridden X (250 and 450) have the overflow tank due to riding in slower conditions where the bike is more prone to overheating ..... basically , same bike in almost every aspect except 1 is a stripped down model and 1 has all the bells and whistles , the only other difference is the X radiators are larger than the R so that aids in cooling as well , but the overflow will work the same on both bikes ....
I know ,
a simple yes would have sufficed