I just did the valves on my 300i dt. at 28.000 km. very easy,. remove the seat and tub , remove one tube , remove 4 bolts and remove gas supply hose by one bolt on top of it, wiggle cover till it comes off, all clear for doing your valves,. mine were tight on one valve onexhaust and one on intake,. now I am looking for a 3 mm. spanner foe adjusting valve, to make it easier to hold while you tighten the lock nut,. reassemble and your done,.