The bike I bought had a bad leaking head gasket, enough for coolant to end up in the expansion chamber (don't know how it ran but it ran ok believe it or not). I have replaced the cylinder and gave it a new top end and runs awesome now. Problem is there was chunks of navy blue crystallised substance throughout the cooling ducts on the cylinder and I have since discover this same stuff has blocked up the radiator cores. Flushing with a hose hasn't worked and I am thinking about soaking the rads in a tub of water with a bit of pool acid.
Anyone else come across this and successfully cleaned the cores?