A few brief notes on replacing a water pump...
You don't need a wooden dowel to knock the old one out if you are going to replace it, and good luck finding a long thin dowel strong enough to bash anyway!
Use a long screwdriver. Make sure you undo the retaining bolt on the other end first though.
The Original shaft was pretty much 10.1mm diameter, while the new one was 9.85mm. Enough of a difference to make a difference!
Use the new seals that come with the pump-they are suited to fit the new one.
Note how they fit. Before removing them-take a photo with your phone.
they can be pressed back in to place easily, when greased, just keep them straight and clean.
Don't forget the special grease, or the spacer that goes in between the seals.
Mixing some kinds of anti-freeze results in a gunky mess/gel around the water pump impeller-so don't be surprised it that is knackered and/or dissolved entirely. It also prevents water from circulating-this is BAD THING TO HAPPEN.
Always flush out the system. Tap water from a hose is fine to flush. You should only use distilled to refill-or the ready mix anti freeze of course.
Don't mix antifreeze types. Flush all the old stuff out and refill-use Nitrite free stuff (so as not to burger up the aluminum engine parts). Eurocarparts sells it ready mixed. https://www.eurocarparts.com/p/triple-qx-orange-ready-mixed-antifreeze-coolant-5ltr-523770981
Don't forget to flush out the header tank behind the seat.
If there has been any mixing of oil and water, best thing is to replace the larger seals on the pump body too. They may not come with the cheaper pump impeller kits.
Take care pushing the new pump back into place, so as not to break the teeth on the plastic cog against the metal cogs. Keep it "square" and push gently.
Remember to fit the circlip (circlip pliers are cheap and make this sort of thing SO MUCH EASIER!
Take care not to break the plastic gear when removing it. I used a pair of mole grips to clamp on and pull, gently but firmly.
If you are careful and lucky removing the generator cover, you wont need a new gasket. If you hang it out of the way using an unbent wire coat hanger or string, you may not need to unplug the generator wiring-which means not removing the side panel.
While you are there, check the generator wires for breaks/continuity.