2006 KX250F Left Intake Valve

[lukesh40]

Bought the bike last summer, has continued to run very well. Checked the valves this past fall, all were in spec except for the left intake was on the tight side. Re-shimmed, now fifteen hours later the left intake has zeroed out while the remaining three show the same measurements as recorded last fall. Also, the left side of the intake cam has residue/carbon buildup while the rest of the cam is clean and shiny. I'm hesitant to re- shim again as I understand this is probably a sign that the valve seat is worn and needs to be replaced, but my question is why the one valve when the others still seem to be in fine shape? I'm still yet to pull the head and inspect the valves/seats, probably get to that tomorrow. Anyone have any suggestions as to what I should do? Pretty crappy to happen so early in the season :think:

 

[Matt90GT]

Time to get the head redone. reface the seats or replace as needed. new guides and seals. And new valves and springs.

The OEM valves are Ti which has a coating on them. When the coating wears off the valve is very soft and will zero out in no time.

You can swap to aftermarket SS units for longer life.

 

[lukesh40]

This is kind of what I figured I was in for, just wanted to hear some opinions. Any idea what it would run me to get the head redone as well as reface or replace the valve seats?

 

[_JOE_]

Right, once the valve and seat start to wear they go quickly. Dirt is the biggest enemy. Pull the top off the carb(the larger top cover you go through to access the needle) when you get it off and see how much dirt is in there. My FCR carb was a dirt sucker for sure....

That being said you should also inspect the air filter seal and boot/box connection. Use a high quality filter oil also.

 

[lukesh40]

Hmm, didn't think about that, good point though. I'll look into it, thanks Matt and Joe.

 

[lukesh40]

Head is going into the shop today to be rebuilt with kibblewhite SS valves and components. Gonna throw in a fresh piston as well and this thing should be a whole new beast! Thanks again for the replies

 

[steve.emma]

one possible reason for it being just the left valve instead of both is check to see if the carb acclerator pump is squirting onto that side of the intake port causing premature wear?
just a thought.