If it's time for the 12,000 mile (20,000 KM) service on your R1250, I'll show you how to check your valve lash without having to buy any special tools. You'll save a ton of money over taking your bike to the dealer, especially since the valves on these BMWs don't need to be re-shimmed very often.
As mentioned in the video, @Boxflyer11 has an amazingly detailed series of videos showing you how to re-time your cams and measure and shim your valves using special, custom-built tools. I'd suggest watching his videos if your valves are out of spec.