Valves without seats?

[0bigsilver6]

I have been doing tons of research and making a list of maintenance that I'm sure needs to be done to my 02 yz426. Changing the valves being one of them. I plan to switch to the stainless set of everything. But is it even worth it to change the valves without changing seats? The valve clearances tighten up because of the wear on the seats don't they? Seems like the seats might be a necessary part of this equation to restart the process of shimming the valves if that makes sense. Is there a way I can replace the seats at home, I'd really rather not have to pay a machine shop to do it if changing the seats really is necessary.

[SteveThe Snakes]

I have been doing tons of research and making a list of maintenance that I'm sure needs to be done to my 02 yz426. Changing the valves being one of them. I plan to switch to the stainless set of everything. But is it even worth it to change the valves without changing seats? The valve clearances tighten up because of the wear on the seats don't they? Seems like the seats might be a necessary part of this equation to restart the process of shimming the valves if that makes sense. Is there a way I can replace the seats at home, I'd really rather not have to pay a machine shop to do it if changing the seats really is necessary.

Normally changing the seats is not necessary and not a good idea. However taking it to a competent motorcycle machine shop to put your valves in is.

[0bigsilver6]

Normally changing the seats is not necessary and not a good idea. However taking it to a competent motorcycle machine shop to put your valves in is.

Alright I won't worry about the seats then. I'm plenty capable of changing the valves out though, thanks for the advice.

[moto867]

Changing the valves is easy enough, but you should have the seats cut to make sure the 45 degree face is flat.

[0bigsilver6]

Changing the valves is easy enough, but you should have the seats cut to make sure the 45 degree face is flat.

This I'm assuming is the beveled edge around the seat you speak of? Just to ensure there's not any divers or dents in the seat?

[moto867]

Yes, the sealing surface gets cupped over time. You just need to freshen up the 45degree angle. Any competent shop can do this easily

[grayracer513]

The valve seats absolutely need to be refinished whenever the valves are replaced.  Normally, YZF seats don't wear much, and will need only a touchup, but it's the only way the valve job will hold up as it should.

 

A really good low cost, high quality option on the 426 is to use the valves and springs from a 2000 YZ426, which were stainless, and as a set are priced well under the better aftermarket SS valves.