Guys my MC18 kinda make a tapping sound specially at idle.. I hear it came from the RC Valve so to be sure, I touched the RC Valve shaft and its positive that it is coming from the RC Valve. so I took it off and look at the Shaft and the RC Valve.. I noticed that it has a little play between the shaft and the valve itself. I dont think that the piston is hitting the rc valve causeif it does it should have cracked the piston by now and siezed the engine. the fact is the bike runs well except for that tapping sound.. is this normal for a 15000 KM engine and if its not what should I do? replace them? if I will not replace them what will happen?

Thanks a lot to all..
ride safe.