Recently picked up a 2006 GSXR 600 (unknown miles, questionable care by previous owner). A friend and I are going through the bike and noticed this build up on the backs of the valves. I am a novice when it comes to bike maintenance, but he is seasoned. Both of us don't know what's on there. So I was hoping you guys could clear this up. Thanks!
It's congealed unburnt fuel. Depending on the type of fuel used and the air/fuel ratio, you get various colors. Looks like you might need a valve job/top end rebuild.
Not that Rick's word needs it but I'll second that. Looks like an overly rich tune and you should consider having that head re-done.
Thanks for the replies guys. Just an update, I pulled the bazzaz to look at the map and there was no map loaded. It was completely blank. Bike has a full yosh exhaust with the cat. cut off and BMC filter. This may explain the valves/ insufficient air:fuel ratio.
I should have a nice, clean head on a parts motor that i have. Low side busted the water pump housing/case like so many on these model year GSXRs.