Yes, that's the order it goes except that you have the damper and holder the wrong way round from what I can see - the rubber face goes into the recess in the back of the impeller. Obviously the mechanical seal assembly needs pressing into the pump body first, then fit the impeller (with it's damper installed).

However... Looking at the corrosion and corresponding abrasive surface on your impeller shaft, I very much doubt that the new mechanical seal is going to last that long! If it was my bike, and I'd got this far into the water pump, I'd be erring on the side of replacing the impeller. You don't want to have to be going through all this again in a hurry!

Corrosion like this I've only ever seen before on motors run on pure water, or with old coolant that has lost its corrosion-inhibiting properties. When did you last change the coolant?

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