Proper technique for sanding shims?

[Grappa]

So I'm doing my first valve adjustment and trying not to    too much.  I'm concerned about my technique because the two opener shims I have done so far required a small bit of sanding to get the clearence right.  When I replaced the shims onto the valves, the clearence was good, until I tried spinning the shim to make sure it moved.  After spinning the shim in its place, the clearence changed.  So I put the feeler gauge between opening shim and rocker (.004") and then tried spinning shim, and it would alternately fit and not fit.  Guess I did not sand it evenly?  Getting a bit discouraged.  I have 2001 M900, using 400 grit paper with wd-40, paper on top of flat plate of glass, making small circles, turning shim 90 degrees, making small circles, turn, circle, etc, measuring often.  What can I be doing better? 

[ducpainter]

So I'm doing my first valve adjustment and trying not to    too much.  I'm concerned about my technique because the two opener shims I have done so far required a small bit of sanding to get the clearence right.  When I replaced the shims onto the valves, the clearence was good, until I tried spinning the shim to make sure it moved.  After spinning the shim in its place, the clearence changed.  So I put the feeler gauge between opening shim and rocker (.004") and then tried spinning shim, and it would alternately fit and not fit.  Guess I did not sand it evenly?  Getting a bit discouraged.  I have 2001 M900, using 400 grit paper with wd-40, paper on top of flat plate of glass, making small circles, turning shim 90 degrees, making small circles, turn, circle, etc, measuring often.  What can I be doing better? 

Try sanding in a straight line turning 180 degrees after every couple of strokes.

Then turn 90 and repeat the 180 turn.

The leading edge always cuts faster, just like brake pads.

Coarser paper (220) will cut straighter.

[bigiain]

Try sanding in a straight line turning 180 degrees after every couple of strokes.

Then turn 90 and repeat the 180 turn.

The leading edge always cuts faster, just like brake pads.

Coarser paper (220) will cut straighter.

I sand in figure eights, turning the shim ~1/8th of a turn every second figure eight "lap". I always check sanded shims several times turning them slightly when I refit them. If you've gotten it wedge shaped enough that it's .004" out, I'd be getting some new ones and starting again...

big

[scott_araujo]

Don't make more than a few sanding strokes without turning the shim.  I like 400-600 paper.  It cuts slower but you're less likely to make a mistake and it leaves a nice polished surface.  WD-40 works fine, use lots of it to flush off spent filings.  Make sure you sand on a flat surface.  A glass plate is good, I use a 12x12 marble tile.  And get a cheap digital micrometer at Harbor Freight tools.  This way you can measure as you go without having to reassemble every time.

Scott

[Desmo Demon]

I've used all of the techniques recommended and start with 220-grit and finish with 600-grit. Just take your time, try not to take too much off too fast, and you should be fine.

[teddy037.2]

+1 on the figure 8s