I'm in the process of a complete rebuild of the bike, and just finished the carbs. It looked very similar like on the previous photos, green residue, etc. My method: complete disassembly, ultrasonic cleaning, replacing all of the gaskets, assembly. The ethanol fuel makes the brass parts pitted, and must be replaced - the jets at least. Found a great source of real viton gaskets long time ago: Litetek. It is a thai company - who thought that the best gaskets will be made in in Thailand?! All in all, I bought gasket kits from them throught the years for my YZF750R, TRX850, TT600R, and now the FZS600, and everything was perfect. I recommend them.For me it doesn't make sense to buy the OEM gaskets - they are not viton, cannot handle the ethanol. And expensive. Similarly, most of the other sellers (Ebay or moto parts shops) offer chinese gaskets, which are also not viton, under different brand names, or unbranded.To prevent the degradation on my freshly rebuilt carbs I never buy "cheap" 95 fuel, it contains 10% ethanol nowadays, instead 100 octane premium which has 5% ETBE (it doesn't absorb water like ethanol). Alternatively, if you are cost sensitive, you can put a little engine oil or 2stroke oil in your tank when filling up with cheaper petrol at the gas station, it will coat the fuel system with a thin oily layer, and provide some protection. And you can feel nostalgic, if rode 2strokes back in the day...