450 Mystery Plug

While out on a ride, the dime sized rubber coated metal plug blew out of the cylinder head of my 2003 WR450. It is recessed into the head just above the header. I can't get my head around what purpose this plug serves. My dealer wasn't able to offer any thoughts (which is a little disturbing).

I am replacing the plug with a new one, but have to ask why the original blew out in the first place, and what the hell does it do?

It plugs the hole left from the old manual compression release system. The TT store sells an aluminum plug that will solve your problem forever (just don't complain about the price) :thumbsup: This is a very common problem. So when your dealer tells you he can't help you You should be "VERY" disturbed and question his competence.:bonk:

If you want a cheaper route another TT’er put the stock plug back in and fabricated a “L” shaped piece that is held in by the bolt to the right of the plug hole and wrapped around to keep the plug from popping out again. If you take this route take care not to over tighten the bolt, it strips out easily. Personally I bought the plug from the TT store for my own piece of mind plus it come in a pretty blue anodized color. :busted:

Well that makes sense! I made up a plate to bolt on the unused lug before the replacement plug came in, but will just order the TT plug to be sure it doesn't happen again. I was riding in supermoto trim on the street with friends, and may never have noticed the smoke if someone wasn't behind me. That would have made for a lovely bang.

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