Oh no, 400 vs 426 again...

[Kurlon]

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?

[grayracer513]

The 2000 426 had the same SS valves as did the 400. If you choose, you can install them in the later heads. However, the Ti valves (that's the OEM Yamaha valves) hold up extremely well also. A good part of their durability depends on the seats being correctly finished, and the guides must be in good condition.

IMO, the 426 is a superior machine to the 400 in every respect, which is not to diminish the number of thing the 400 is superior to.

[Kurlon]

Ok, so I shouldn't be scared of the Ti valves then, well that makes things easier. : )

Anyone got the actual numbers for the weight difference between the 98 400 and 02 426?

[razornpc]

i think my 400 was 268 wuth gas (tank), loved the bike though. just wasnt what i needed for tight woods.