Valve Shimming

5 replies to this topic
  • Matthew12816

Posted May 28, 2014 - 03:53 PM


i'm currently shimming my valves on my 05 YZ 450F. My exhaust side are all in specification. But my two intake valves(the two closest to the carb) were out of specifications(it was more than my biggest feeler gauge which is 0.25) and i put the biggest shim i have in my kit which is a 3.50 and it is still out of spec so any help here would be very great... i have no clue what to do at this point?



The recommended intake specification are 0.010- 0.015


The recommended exhaust specifications are 0.020- 0.025

  • Slow and Jerky

Posted May 29, 2014 - 04:03 AM


Check the cam lobes with a micrometer, also take a close look for cupping on the lifters.

  • grayracer513

Posted May 29, 2014 - 06:34 AM


The likely cause of this is either that the valve is sticking down off its seat due to carbon on the stem, or that the tip of the valve stem is broken off or mushroomed over.  It could also be that the valve is bent.


If it's carbon/sticking, you can often free them up by tapping judiciously down on the lifter to make the valve bounce back and snap all the way back shut again.

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  • Matthew12816

Posted May 29, 2014 - 07:55 AM


Alright thanks for the ideas I will try that when I get off work tonight and keep you guys updated

  • Matthew12816

Posted May 29, 2014 - 01:46 PM


Alright there was a little bit of carbon on the valves that weren't making them close right so I cleaned them up and got my bike back together but now my bike wont start

  • Matthew12816

Posted May 29, 2014 - 05:43 PM


And before I put it back together I checked the timing and the valves where is specification

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