Remove the the printhead and flush from the cartidge side and and output jets side with running hot water. Alternate front to back to flush out as much ink as possilbe. Then let the print head soak in water over night, then flush again. I do this with all my Canon print heads, there is nothing to damage with water. Just don't touch the print head jets with an object or dry them off with a cloth as the jets are easy to damage. Blow the printhead off with caned or compressed air when you are done flushing. As a last clog removing attempt after the water flush, spray the cartridge input ports using Windex with "Amonia", also spray the jet side with the Windex also and let soak, then do the water flush again. If after all this you still have clogs, then time for a new print head or printer.