Hello all. I have the good fortune of having a couple Yamaha four strokes potentially available to me to use as a base for a GP Mono build. Think supermotard wheels, but lowered front end and possibly street bike bodywork. The two machines I'm considering are a 1998 YZ400F, and a 2002 YZ426F. From reading, the 426 has an updated crank, crankcases, CDI, steering head angle, and a lighter subframe and swingarm, on top of a bit more hp than the 400. It's also got Ti valves, and I think thats the one thing that really has me hesitating on going with the 426 over the 400. I'm going to be road racing the motor, so it'll be spun up and held there for long periods. The 400 has steel valves, which I'm confidant will hold up, the big question for me is how well do the Ti valves?