Hi I'm a new rider, just bought a '95 ls650 with 4200 miles on it  last week and am learning to ride. I was having lots of afterburn, was running hot, and it was really sluggish at the low end of second gear. From reading the forums I figured this was from the fuel mixture. Someone had thoughtfully already pulled the plug over that screw so I was able to open it up a bit so it'll idle smoothing with the choke closed all the was and can rev it up without it backfiring at all. I'll take it out for a ride tomorrow to see if it's still sluggish and trying to over heat.

But anyway, while I was adjusting the fuel mixture I noticed the plug just below that screw is encrusted with some kind of black crud; is this a sign of anything I should be worried about?
Everything else looked clean aside from some tarnish and bluing on the bend in the exhaust pipe which I assume is from the previous owner running it hot for the few thousand miles he put on it.

Sounds good, I'll break out the toothbrush.

I use Berrymans B12 this will knock the crap outa any thing in there.

http://www.berrymanproducts.com/

That would be because it has M.E.K in it. That is some nasty stuff. But it does work really well and it is tons cheaper than Seafoam.