08 YZF 450 The Gap?

5 replies to this topic
  • gregory25

Posted March 04, 2009 - 04:21 PM


Ok guys, I got three thousands gap on my intake valves(book calls for no less than four ) and my exhaust valves have seven( book calls for no less than eight). This is the first time i have checked the valves, i have 25 HR's on the bike.Is it possable it came from the factory with that close of a gap or has it wore that much? Will the valves seat a little during break in? Let me know what you guy"s think. Thanks.

  • grayracer513

Posted March 04, 2009 - 04:37 PM


You're certain you don't have .004 and .008" ? I ask because feeler gauges are by their nature somewhat dependent on your interpretation of the correct "feel". There should be a slight drag.

It is reasonable to see one or two valve seats settle this much from a new build, but it does not usually happen.

Yamaha builds to as close to .10mm and .20mm as they can, and use shims in .01mm increments to accomplish this. Inasmuch as neither of thes number are "quite" as large as the rough English equivalents (.004/.008) (bigtime hair-splitting, I know), a slightly snug .004 and .008 is acceptable.

  • gregory25

Posted March 04, 2009 - 04:50 PM


The three and seven have a medium drag, i cant get the four and eight to go.

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  • grayracer513

Posted March 04, 2009 - 05:02 PM


If you're sure of that, you should adjust them.

  • gregory25

Posted March 04, 2009 - 05:42 PM


Im sure, thanks Gray.

  • MikeyT750

Posted April 21, 2009 - 05:21 PM


I have the same thing going on here. It's an 08 YZ450F and my 1st Motor Blew up right after the new year. Needless to say, I am a little paranoid about the whole Valve Clearance thing.

This motor has 20Hrs on it. So I decided to check.

L EXHST is .17
RT EXHST is .20

Far L Intake is .08
Middle Intake is .08
Far RT Intake is .10

Did you end up re-shimming? I got a race on Sunday so I got to get it on it ASAP.
One other thing, there was someone that said that the Cam Cap screws Torque Spec is a little tight according to the manual. If you did re shim what spec did you torque the caps down to?
Thanks A Lot!

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