What defines a proper valve clearance measurement?

My question is, what defines a proper clearance measurement? I am doing my first valve adjustment of my life, learning as I go, and I am encountering varying degrees of clearances, and resistance to the gauges. If a gauge can be pushed in period, would that gauge size be the proper measurement? For example, say I hypothetically could not fit, no matter how hard I pushed, a .15mm gauge, but I could fit a .14mm gauge, albeit with a good degree of sticking and resistance, would the correct measurement of the clearance be .14mm?  Or, is the proper measurement when you encounter no resistance to one gauge, say a .12mm, then a slight bit of resistance and contact with a .13mm, and then more significant heavy rubbing with a .14mm.  Would the correct measurement be .13mm because it was the first gauge to encounter resistance?  

You should feel a light resistance when the gauge is pushed through. In your example the .13 would be the correct clearance.

Plus one on that 0.13.  It can be tricky, a critical step is to make sure your guage is flat (Parallel to the gap surfaces) as it enters the area to be checked.  Thier are bent guages for this, or very narrow  guages that can be used that are quite bendy, or you can bend a few of your favorite ones LOL.  If you use your finger to push down on the feeler guage  where it enters the gap to be checked you can hold it pretty parallel  (finger tip needs to be in far enouth to be in the plane of the gap (hope I explained it right)).   If it binds and scrapes, IMO its too tight.  Its very common to have one size that's "tight" and one size down is "loose".  Which one to choose?  Depends on spec, it both are within spec fine!  If the tight one is on the upper end of the spec sure shim it down if you like and next shim will bring it in spec.  Or Just pick one  measurement and write it down with a note eg  0.14 mm-tight, for next time.  check clearences more than once to insure your teckiniqe  is good.  Chekc, record, kick engine over and check again.  Once you are consistent then you know your doing it right.  I have spent many many hours doing this over the years and quite frankly have the same kinda qustions in my mind still, just paranoia really!


Its very useful to know what shims are in the bike already so record them so that when you check your clearance and its out, you can run to the shop and get the right ones (hopefully).  However, funny you should ask.  I got some hot cam 2,25 mm shims this week (rmz450),  measured them with my calipers and they were both 2.20.  I know my calipers are good (new) and match some other shim size stamps perfectly.  So I generally write down the caliper values as well as the stamped shim size, to get the most accurate selection of shim to use.  Ie if you got two that are marked 2.30 and you really want a 2,29 to get the "perfect" clearance, use the thinner one if thier is one.  Measure a few, Good calipers can be found for 20 bucks or so and are very useful and are a tool that if treated well will serve you many years!


Remember, these thoughts are really just my opinions.  Some may even say that this measuring of stamped shims is overboeard.  Probably is!   I'm sure there are other ways, even philosopyies behind shimming.  One guy likes to lap them on sand paper and a perfecly flat surface to achieve the excact lower value of the range.  Cool I figure, other guys says don't mess with your shims.  Both are probably right, providing that guy one can achive a perfectly "machined" shim.


Key is, is it in spec?  If so fatso your fine.


Don't you just hate it when the manual says, check for "excessive" play or wear  WTF is that.  LOL

Edited by bikedad1

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