Just a tip for anyone who's got a twin plug head.
(On the bike that is..)
I was replacing the inner plugs during a full service on my Norge. The tank and air box were removed for another reason and I thought I'd blow 140,000 k's worth of accumulated crap away from the valley between the cylinders.
All good so far..
As I was blowing the air around the inner plug on the left side, I happened to look down into the "tunnel" that the plug resides in, and there as large as life was a stone about the size of a piece of rice or corn, leaning at the base of the plug and would have fallen in the cylinder for sure, had I just whipped the plug out...Close one..

Also it became apparent that last time I'd fitted new inner plugs, I'd used a plug socket that did not spin freely in the tunnel, and when I thought the plug was snugged down, it was actually the socket that was resisting the turning, resulting in the plug being a bit short of fully home.
You could see the grubby few threads down near the chamber, when looking into the head with a strong light.
This is bread and butter stuff for a real mechanic, but I got caught...
