As the title suggests. Fairly thin and solid, wont come off in any quantity with a cloth but a bit of carb cleaner and a wipe and its gone. Its only in the secondary inlet port. Iv given it a clean and Il check again fairly soon but in the mean time any suggestions what the residue could be or the cause?
Thanks guys!

I also had this on my TTR600
I think it may be normal,bike runs ok
Will post a pic if I can find it

If its only the secondary, must be when its on small throttle opening & the secondary is still shut, therefore has low pressure in the port, so any blow back (at valve overlap) entres & leaves a deposit?
Interesting............ never thought much about this one!

Thats an interesting idea. The set of carbs I got, not from this engine, also had residue on the secondary butterfly. Problem is my Srx400 engine has clean inlet ports

Could it possibly be oil from the engine breather? No idea of teh plumbing on your bike.