HEADS UP!!!

Site upgrade in progress... Core site functions are working, but some non-critical features/functions will be temporarily unavailable while we work to restore them over the next couple of weeks.

Please post any bugs you encounter, but before you do, check to see if it's already listed.

Thanks for your patience while we work to improve the community.

Sign in to follow this  
Followers 0
hillclimb426

Intake Valve clearance to large?

10 posts in this topic

Bike is a 08 450 . Bike has always started on first or second kick. Runs great. So I checked my valves and they are all in spec except the right intake (closest to exhaust ). It measures .35mm. Seems a bit far out to me. What can cause this ? Carbon ,weak spring , bent valve.

Share this post


Link to post
Share on other sites

you got it. carbon build up on the valve or the seat.

i believe you can tap on the valve stem lightly to try to jar some loose. i dont have expirence with that though, i know Gray can comment on that better.

Share this post


Link to post
Share on other sites

First be sure the valve is seated as mentioned above. If the excess clearance condition persists, inspect the cam cap for seizure damage, and the top of the valve stem for mushrooming.

Share this post


Link to post
Share on other sites

Ok I will try this in the am and see what happens with the clearance. I measured the shim several times and get 1.70mm with the micrometer. Doesn't seem that it is wore in the center. I'm pretty sure I must take the valve train off to see if the valve is seated? Or could I cheat and look through the exhaust with flash light to see it? Maybe have a budy turn the engine over wile lookin in ?

Share this post


Link to post
Share on other sites

You're not going to be able to tell by looking where the extra .10mm (.004") went. Use a punch and a small hammer to tap lightly downward on the suspect lifter, allowing it to bounce back against the seat freely a time or two, then recheck the clearance. If the valve is sticking, this should seat it.

Share this post


Link to post
Share on other sites

Ok I tapped on the valve and rechecked the clearance ant it is still the same...had my gf stop and pick up the shim the table called for at this clearance. Check it again and got .35mm ? I guess I need to pull it apart a clean the valve seat ?

Share this post


Link to post
Share on other sites

I would say you're doing something wrong if the clearance is the same with two different shims.

Share this post


Link to post
Share on other sites

I have measured it several times and not my first time checking. I may have measured the shim wrong though. At least i know what shim I have in there now I guess. I will take a look at it again. Still seems odd that intake valve is so far out. If it is carbon on the seat why would it only gather around one and not all. I did have a dumb wreck the last time i rode it and blew my knee out. The bike was upside down on a small hill running until it stalled. Could this have allowed a piece of carbon to get stuck in between the valve and the seat? Then the ride home beat it in place ?

Share this post


Link to post
Share on other sites

The center intake runs twice as clean as the outers because it gets hit with most of the fuel in the f/a charge. The carbon, if that's the cause is more likely on the stem where it meets the guide.

Share this post


Link to post
Share on other sites

I finally got a chance to check everything again. Triple checked timing and tdc. Clearance was the same on the righ intake . So I pulled the cam again and decided to pull the cap off the center valve to compare stem height. Found problem the keepers were out of there groove on the valve stem! They were almost to the top of the stem! So I pulled out the offending valve and cleaned it and the valve seat. Witch looked good and the valve is seating correctly. I ordered a new spring and keepers and head gasket. Impatiently waiting for there arrival! At least I have another bike to ride this weekend.

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!


Register a new account

Sign in

Already have an account? Sign in here.


Sign In Now
Sign in to follow this  
Followers 0