GY6 exhaust valve corrosion driving me nuts.

[Robert3165]

I have a GY6 scooter, a 150cc (SUNL). It has 3k miles on it. My issue is the exhaust valve corroding with resulting loss of compression because the valve isn't seating properly until it quits. This is the second head I have installed on the machine (returning the old one when it failed). The valves are properly adjusted during install and the scooter burns nonethanol gas. What I cant figure out is rust and corrosion build up on the exhaust valve within 300 miles. The scooter has been taken on about 25 mile trips so its getting up to temp. I am now down to trying stainless valves. Has anyone else had this problem??

DSC03174.jpg

Picture is kind of blurry but you can see the exhaust valve on the left and the rust/corrosion build up. I should also say the plug is clean and tan.