Intake Valve clearance to large?

9 replies to this topic
  • hillclimb426

Posted February 07, 2013 - 02:29 PM


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.

  • DC_Excitement

Posted February 07, 2013 - 02:46 PM


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.

  • grayracer513

Posted February 07, 2013 - 04:03 PM


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.

  • hillclimb426

Posted February 07, 2013 - 09:10 PM


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 ?

  • grayracer513

Posted February 08, 2013 - 07:30 AM


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.

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  • hillclimb426

Posted February 08, 2013 - 05:50 PM


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 ?

  • grayracer513

Posted February 09, 2013 - 06:16 PM


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

  • hillclimb426

Posted February 10, 2013 - 09:19 PM


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 ?

  • grayracer513

Posted February 11, 2013 - 12:39 PM


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.

  • hillclimb426

Posted February 23, 2013 - 08:23 AM


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.

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