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I'm doing a valve adjustment on a 2011 CBR250R. I've got the lash and current shims measured.

Both exhaust valves and one intake valve were tight. I thought it would be best to order shims that would put my valve lash slightly under the upper end of the spec (IN: 0.19mm, EX 0.30mm), Since the valve lash tends to get tighter over time instead of looser.

After ordering new shims both exhaust valves should be around 0.28mm and intake around 0.18mm. I could order the next thicker shims (+0.025mm) and be closer to the center of the spec (IN: 0.16, EX: 0.26).

Any reason to choose one over the other?
 

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As you've discovered, valve-clearance tends to tighten with wear and age. This is caused
by valve-seat wear that causes valves to sit deeper into seats. Go for shims that sets clearance towards larger end of range. Gets you most time before next adjustment. Also wards off potential for fried valves if next adjustment isn't done in timely schedule.
 

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Honda: INNOVA125i(2010); CBR250R(2013)
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Since the valve lash tends to get tighter over time instead of looser.
Hi
NO
To the best of my knowledge it is the opposite:

As the wear increases, a thicker shims need to be added, meaning the spacing increases and should be reduced by thicker shims.
Increasing in the valves gaps due to wear, this is what also makes the noise of the valves that ticking louder, the so-called: "UnAdjusting valves noise"

If you have reached the opposite conclusion I recommend that you repeat the test one more time. Maybe a calculation error?

And since the tendency is to increase the wear, which increases the free play, and if you want to aim at the upper limit, then you should order the thickest shims that possible, (and not the thinnest)
 
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