I see Munich BMW in Perth offer a water pump shaft without the gear, so requires the old gear removed from the shaft and pressed onto the new shaft. Rebuilding the water pump is within my capabilities having learnt a few years back how not to do it the first time around, but I am wondering if changing the gear over to the new shaft is above my pay grade having not ventured into this territory before, and also thinking specialised equipment (a press) is needed which definitely counts me out, so would have to find a shop to do it. There is a significant cost saving depending on what I’d be charged in labour. Anyone gone down this road?

Didn't know the gear was pressed onto the shaft  .

But, if it is then heating it up should have it dropping right off.

@kiwik100 - did you manage to change just the shaft ?
I’m in similar situation..

Yep, I bought the replacement shaft from Munich in Perth and had an engineering shop remove the old shaft and press the gear onto the new one. 20.00 well spent I think. I’ve rebuilt the pump and installed it and while a small amount of coolant leaked through the weap hole, this has all but stopped now. I enquired on the forum about it and those with lots of wisdom suggested to leave it alone until I have the engine running and the seal will then bed in fully. I've not posted how it all went as I’ve not had the bike running yet due to still restoring it. However I’m only waiting on the tank and panels to come back from the painter and it’s all done. I’ll update with pics when it’s finished.

Thx mate - will do the same then.!

I bought the pump repair kit from Motorworks in the UK for AUD50.00 and the impeller rotor and bolt from Munich for AUD40.00 along with the shaft for AUD150.00. This was the most cost effective way, but remember if you spend more than 200 quid, or the parcel ways more than 2kg (I think that’s the weight limit) then they won’t sent it by Royal Mail which is cheap as chips. Instead it goes by UPS I think which is very expensive.
Munich don’t do a pump repair kit, so every part has to be bought separately which makes it way more expensive.

I’ve got the overhaul/repair kit - didn’t think I needed the shaft, but clearly I do . Sometimes we think wishfully

Finally got the engine running last night and I’m pleased to note that the new pump rebuild has sealed nicely and there is no drip from the weep hole.The shaft from Munich MC  in Perth fitted perfectly and a considerable saving on buying a new shaft and gear assembly.

How did you know you needed to replace the shaft? Just opened up the water pump housing and the shaft was worn? I have some coolant drip out of the weep hole and looks like I need to rebuild to pump.

If the shaft is worn where the seal sits, you likely need to replace it; else things won’t seal well (for long)

You should be looking for pitting corrosion around the shaft.  A little bit will be okay and always worth cleaning it up whilst in there.  

The seal will be old and simply needs replacing.  

I keep a couple of small drills bits to clean out any gunk in the weep hole.  Turn them by hand, obviously.

Sorry a bit slow getting to this - away riding. Answers cover everything anyway. Shaft is generally pitted and full of muck, and cleaning it will make it leak more if you install a new seal kit onto it. Don’t ask me how I know this…