Hi everyone

I am attempting to replace the seals in the water pump. I have the cast impeller and have purchased the original water seal.
Unfortunately I broke the threaded section of the shaft when I hit it with a hammer to try and remove the impeller from the shaft.😢
The shaft is in good condition and was wondering how necessary is it to install the nut?
The cast impeller is an extremely tight fit on the shaft and I'm thinking would that be enough to to ensure the impeller doesn't move?ive heard of cases where the nut breaks off but never the impeller.
I was thinking of drilling out the remainder of the shaft and installing a screw or perhaps jb weld the broken section of the shaft all opinions  
Will be appreciated.
Cheers

It will come loose and not pump with disasterous concequences or will work it's way forward and saw it's way out with disasterous concequences. Coming loose is the most likely and the most disasterous.
Bite the bullet and get a new shaft.

I'm Thank you for your response. I appreciate your concerns but I'm not entirely convinced about the situation I have the earlier version impeller and I noticed it requires a lot of physical effort to reinstall the impeller on the shaft.
There was a discussion about this Topic posted a few years and although the nut came loose, the impeller stayed in its original position.
Has Anyone come across a situation where the cast iron? Impeller has detached itself from the shFti might be grasping at straws but I want to give it a go.
What about using a strong glue to reattach the broken section?
I own three original design water seals and I want to at least try an alternative to spending another $200.00
What about drilling out the remining threadedsection and attaching a screw?

Cheers

If you want to try it give it a try.

AFAIK the only reason the early impellers jam on the shaft is because they rust there. You can't rely on that happening in a hurry. Drilling and tapping might solve the problem but make sure you Loctite (or similar) the screw in. I can understand the reluctance to spend another A$200 for a complete s/h pump (Motorworks) but that's what I'd do.

As a purely personal opinion, I don't like the early impellers. They can and will turn into a big blob of rust that won't pump anything properly. Evidently BMW decided they didn't like them either because they changed the design for something lighter and more efficient.

Thank you for your advice.
I understand your concerns but the stubborn side of me wants to persist with this situation.......
Is there a glue with enough strength for me to rejoin the broken bit?
My impeller has been in my bike for almost thirty years and there is no rust on the impeller....and I've got three of the earlier version of water seal I don't want to throw away.....
I prefer to try and reattach the broken piece by using glue....

I don't think there's a big enough font on the forum to shout 'no' to the glue idea

I'm with Dai as regards a 'no' to trying to glue the broken piece back on but I'm with you mate in relation to sticking with a design that allows you to make use of the spare seals you have.
Why not take the shaft and impeller to a machine shop and get them to measure with micrometers, the relative sizes of the impeller bore and corresponding outside diameter of the shaft section that engages in this bore. Ask them for repair ideas / price estimates and keep us posted.

Have you got access to anyone with home machining capability? If you decide to throw in the towel, persuade a Brisbane based Forum member to visit Ray Peake  and grab the pump unit of my '83 K100 parts bike. You may need to pay Ray commission as he is wanting to charge me storage. (He's already had some storage money as I noticed on my last visit that he had helped himself to the monkey nuts from the alternator drive - presumably for a paying customer).

Hi

After much procrastination, I made a few enquiries and was referred to the ktm motorcycle dealer in werribee melbourne. 
The owner has a workshop setup in the rear of the premises including a lathe.
He replaced the threaded section and I was able to replace the seals.
This guy was helpful and charged a very reasonable price for the job.

everything seems ok so far...I am a little concerned about the effort required to spin the impeller.
Thanks to all who replied to my post.
I will let you know how it goes after I install the pump.

Fingers crossed!!!!!

Cheers