Had a surprise the other day when I noticed crankcase paint flaking around the water pump. Am suspecting WP gasket. OEM hoses are 31 years old, but still pliable. Premix coolant used, no tap water. Most likely reason for the corrosion?
It looks to me like coolant which has slowly seeped out and crystallised. It also looks like it was green which, if so, implies it’s probably an ethylene glycol based coolant with added silicates. If that is the case it can, when in contact with aluminium and air, corrode the aluminium. The water pump junction and housing and crankcase cover are all an aluminium alloy. If it were me, I’d drain it, flush it thoroughly, repaint the damaged areas and refill with a modern OAT coolant such as Motul Organic+ (there are plenty of other OAT options).
Many thanks for the diagnosis and solution. 100% correct- I've been using a generic green coolant for the last 7 years. Was clearly unaware of the consequences of doing this.
Not your fault really, I think that’s what was in use, and what the factory used, back in the ‘90s so it’s perfectly understandable one continues with the same. OAT coolants really only became generically available after the 748-998 range was past production.
Some of your corrosion looks likely partly due to storage conditions sadly. After 7 years nothing less than a perfect/stable temperature environment will do this eventually anyway and it can still be hit and miss depending on where it's stored.
Have replaced coolant every 3 years on average. Bike is stored in a fairly dry garage, but huge temperature swings here between summer (+35°) and winter (-25°), which might help explain it.
