I bought the shims, gaskets, feelers, etc. and have been getting up the courage to check the clearances on my 05 WR450. I've got about 800 miles and it starts great with hardly any need for choke, runs great but I decided it was time. All valves within tolerance although on the tight side of the ranges but I decided to let them ride for now. I'll probably check them again after another 500 or so miles just to be sure but I sure was glad not to have to do the shimming. One question I did have though was about the spark plug. This is the first time I have had the plug out (and hope I never have to change it on the trails) and it was really rusty which tells me water is getting in around the cap. I don't ride in severe water conditions so it must be from just washing. I don't use power washers. Is this common? Should I put some silicone or something around the seal?