If we know that valves control the flow of air and fuel, into the cylinders and exhaust out of them. And when and how long the valves open (timing) and how much the valves move (lift) both affect engine efficiency. Did you noticed eny increase in fuel consumption whan you have to adjasting valves? I did not whith 45 000 km on my odo. I ask because I whish to skip open engine and checking valves.

Hmmm sandro... I think checking valves is a maintenance task that needs doing. The book says every 20,000 km.

I have to admit that I've never noticed any improvement in a bike's operation after having done it. If the engine rattles a lot the work may need doing, but the bigger problem imo is if there is not enough clearance. Eventually this can be expensive ie burnt valves.

A few hours of work for peace of mind is worth it, I think.

I fully agree with 66T. The first time it take some time, but now I can do it within an hour. Loose valves you hear but tight ones are quiet, but cause more damage.