Hi everybody,
I'm very surprised that, apparently no one has made this before or at least none has reported it. After searching in my Spanish site and also in this one, I haven't found any reference about this matter and this fact has driven me to make this post which I hope, will help you to fix the water-oil pump cheaper than before.

While repairing my 87 K100 water-oil pump I found that, the main shaft was completely corroded in its middle part so, it wouldn't be possible to reinstalling again without having same leaking caused by this.
I was totally resigned about buying a new one but then, after a deep degreasing, I realized that it wasn't made in just one piece, they were two. So that I took it and with a press I took it out the axel from the gear easily. The next step now is asking for a friend of mine to make a copy of this with a lathe. By my friend's own words, that's not gonna be a big deal to make a new one even the 6mm. allen socket in its widest end.

I have heard of a person in Melbourne Oz who puts a stainless sleeve on the shaft but haven't been able to get to him yet.

I was told about doing something similar to what you say, and also about reducing the axel diameter with a lathe just a little and covering it with a thin hard-chrome bath but I think that it would be easier, chapest and faster copying a new one.

Hi there.
When I did mine, the axle rebuild was an option but after comparing costs, the new one was cheaper. That may be not true nowadays.
I would think on making the copy out of stainless steel if can determine and find the right alloy for the working conditions.
Best regards
JAP

As Japuentes says, ordering to make a new one might be more expensive than buying it but if you got the chance, I mean a fella who has a lathe or so, won't be difficult to find out a proper piece of stainless for doing a new axel.

Hi Domingo,
Put a post in the engine section about this where it will get fully explored by all, once you have done it we will all look forward to a lesson from you on how to do it.
Regards,
K-BIKE

Actually, this was my first intention at the beginning but, I thought it'd be better to do it after getting the whole think ready for mounting as you've suggested in your post. Still I haven't got the new axel, I'm looking forward to get it but I've to be patient cos my friend is currently recovering from a splinterbone break and apparently he won't start working until mid-March.
Let's see.

Good on you Domingo,
This section is reserved for articles from members telling other members how to do a specific job, a knowledge base you could call it and we will all look forward to reading your tutorial "how to". The splinter bone break sounds nasty I hope your friend recovers OK.
Regards,
K-BIKE