Inlet Valve Diagnosis

[waynus]

Was cleaning my air filter recently and noticed a thin layer of dust accumulated on the plastic ducting.

The way I see it, some dust is always going to get in, as SC pointed out (at an inappropriate time). After all, if air gets in, some fine dust must also get through the filter.

This led me to believe that the dust at velocity acts like a mini sand blaster, removing what I have been led to believe is a titanium coating on the valves. Maybe once this is removed, then the valves start playing up. Of course, the exhausts wouldn't be subject to the same abuse and are spared the humiliation.

This could explain why street machines such as R1's with similar revs don't chew valves cos they're not sucking dust.

This would also explain why CRF's are having a worse case of it cos they're always sucking the WR's dust.

I'm more or less convinced that dust is the prime cause of failure combined with modern valve material, but I can be swayed.

The moral is "always ride up the front"

[clark4131]

The way I see it, some dust is always going to get in, as SC pointed out (at an inappropriate time)...

Why inappropriate? Because everyone with an '07 was climbing out on the ledge due to the hole in the filter cage? I just didn't see the need to crawl into the fetal position and go all "chicken little" on that one. Fix it and ride, just quit sniveling ...SC

[waynus]

Why inappropriate? Because everyone with an '07 was climbing out on the ledge due to the hole in the filter cage? I just didn't see the need to crawl into the fetal position and go all "chicken little" on that one. Fix it and ride, just quit sniveling ...SC

Sort of like we've stuffed up on your air filter and it has done long term damage to your motor, how much or little we don't know but it will eventually come out of your pocket so just take it like a man.

Inappropriate time cos dust getting through an oiled filter and dust getting through a factory bungle are two different things. One should be at my expense and the other at Yamaha.

[clark4131]

I still don't understand why my comments were inappropriate...SC

[SXP]

I still don't understand why my comments were inappropriate...SC

'cause instead of consoling and sympathizing with us, you told it like it is:cry:

Just for the record, even with an immaculately oiled filter on my 400s, if you look closely at the screen on the cage it always seems to have a very light coating of light brown (dust) after a good long dusty ride, and the internal walls of the duct also have a very fine coat of dust - it never passes the white glove test.

[waynus]

Just for the record, even with an immaculately oiled filter on my 400s, if you look closely at the screen on the cage it always seems to have a very light coating of light brown (dust) after a good long dusty ride, and the internal walls of the duct also have a very fine coat of dust - it never passes the white glove test.

Exactly. That is my point (and SC's as well) The pores of the foam filter are say 1/50th of an inch. They rely on the incoming air to change direction several times and for any dust to be caught on the sticky oil inside. Well not all the dust is going to be caught and (in my opinion only) the dust is sandblasting the inlet valves on the way in. Seems if this is the case, then stainless relappable valves may be the way to go if utmost performance isn't paramount.

[kyle797]

I really do not think the dust is "sand blasting" the coating off, rather the valve is closing with debris between the valve face and the seat which cauces the hard coating to be chiped off. This leads to ti valves "tulping" which allows the valve to migrate into the head. when this hapens in stainless valves we see small pits in the valve face and stainless can take this abuse i rarely see a stainless valve tulip. i encounter this same thing with stainless valves in road race bikes

[Indy_WR450]

It is very well known that dirt bike engines dont last as long when run in dusty enviornments. No filter is perfect. Even if you dont see a little dust behind the filter the fine stuff is getting through and sand blasting the valves and piston. that is why top ends on dirt bikes are re-done way more often then street bikes. You have to pay to play!

[ckulzer]

I smear filter oil inside my air boot in hopes of catching some of that airborne dust that made it past the filter.

Chad

[waynus]

I smear filter oil inside my air boot in hopes of catching some of that airborne dust that made it past the filter.

Chad

That's a good idea. Every little bit helps.

[thumper tom]

Whats the first word in our sport , DIRT, then BIKE==---=== DIRTBIKE

deal with it

[TooFast]

Better not try a K&N then - they pass lots more fine dust.

This is the reason I am liberal with my filter oil on foam

[waynus]

Whats the first word in our sport , DIRT, then BIKE==---=== DIRTBIKE

deal with it

Some of us like to discuss how we can make our motors last longer, so that we can enjoy riding more without unnecessary expense.

Deal with that.