Its one problem of having the rad blocking view of headers. My 7 yr old 35 k miler is in better nick, but still is getting that way. I did a deep clean of the engine recently and found deep crud. I used a steam cleaner, and it struggled ! ....maybe its a biennial rad off jobby to do a deep clean. I reckon getting my bike treated by slick has helped keep it relatively corrosion free. Plus I dont do wet riding except on bike tour !