tight valves

[dead eye 00]

The last two times I have checked my valves the intakes have had .002 clearence on both sides and the exhaust side has been perfect. I clean my air filter after every practice or race and change my oil after every two practices or practice and a race. I was just wondering what other people have ran into when checking their valves because this does not seem right to me. Also, yes I have it on top dead center on the compression stroke when i check them.
Thanks, Matthew

[GPracer2500]

Originally posted by dead eye 00
The last two times I have checked my valves the intakes have had .002 clearence on both sides and the exhaust side has been perfect. I clean my air filter after every practice or race and change my oil after every two practices or practice and a race. I was just wondering what other people have ran into when checking their valves because this does not seem right to me. Also, yes I have it on top dead center on the compression stroke when i check them.
Thanks, Matthew

In my experience (no matter what engine), the intake valves are usually more likely than exhaust to be out of adjustment. And they generally go tight.

I believe this is because of teenie-tiny particulates that make their way through the intake filter. They errode the valve and valve seat faces as the intake air rushes past. When these surfaces wear it allows the valve to seat higher up into the head which is why the valve lash clearence gets smaller. That's the only explination I've been able to come up with that explains why the intakes seem to consistantly go tight...

AFAIK, anytime valve clearences change it's because something is wearing.

[dead eye 00]

Thanks for the reply. I understand how and why the valves and seats wear, but I have been told that the exhaust side usually go out of spec quicker due to the heat. This is my first high performance four stroke so I am trying to learn as much as possible. When I tear it down this winter I know I need to replace the valves because I am getting down to my smallest shims, but how do I tell if I need to have new seats cut.
Thanks, Matthew

[GPracer2500]

I know it seems backwards that the intakes would need more adjustment. Seems like the extreme heat subjected to the exhaust valves would cause them to go out of wack first. On my bikes/quads I've never found that to be the case though [shrug]--it's usually the intakes that need the most attention.

AFAIK, the only way to really evaluate the valves and valve seats is through visual inspection. Here's part of what the OEM service manual says about it:

http://img47.imageshack.us/img47/4821/450rvalvesyg0.jpg

[dead eye 00]

Thanks, You anwered all my questions.