Originally Posted by Dr. Strangelove
good idea, but how will you know which to order? Is there enough difference in thickness that it's obvious which one it should be? Why are they available in different thicknesses? Does everything else around the shim also wear?
Valve shims do not wear, they compensate for the items that do wear (valve face and seat, cam and followers) and normal variances in production, they make it easy for a manufacturer to precisely set valve clearances during assembly and provide a solid means to adjust those clearances throughout the motorcycles service life.
Back in May I measured the exhaust valves and all were at 0.34 mm, which is as tight as you want them to be, specs are (0.34...0.41 mm) when I pulled and measured each shim three were at 2.00 mm and one was 1.98 mm I recorded this along with their position in the head.
The intake valve clearance was measured at 0.13 mm on three valves and 0.14 mm on the one, specs are (0.10...0.17 mm) the shims were measured at 2.18 mm on three valves and 2.24 mm on the other, these intake valves are right in the middle and will probably not need to be adjusted for a long while.
Valve shims are available from BMW in increments of 0.02 mm ranging from 1.72 mm to 2.40 mm at a cost of about $7 apiece, the dealership I use had very few of them in-stock.
When it comes time to swap out exhaust shims I know what size the oem shims are and will order three 2.02 mm shims and re-use one of the 2.00 mm in place of the current 1.98 mm to make the necessary adjustments since valve clearance is reduced with normal wear.
I checked the cam-timing at 12,000 miles and was a bit surprised that it was off, either not correctly set at the factory or there is a significant amount of initial wear-in. I have since checked it every 12k miles and it has been spot on, the engine runs noticeably smoother with this setting correct.