Hi Folks
 
I’m‘ working on a K100 cafe bike, 1985 and the water pump is giving me hell big time. I wanted to rebuilt it and I have found out a few weird things.
 
By pump has been the one with the cast iron impeller. Originally with the shaft that had a screw going in through it (female) but the bolt got broken inside so I decided to buy another one and the only one I found on ebay is the type with the screw already built in in the end of the shaft.
 
Here is the rub, I have the shaft with the screw built in at the end, I installed the lip seal no problem. I got the water seal, see picture and got it in with no problem. At this point I have the seal installed so that from the impeller side I can push and action the spring on the seal. I’m happy, no cursing so far. Now I oil a little bit the shaft, and proceed to install it. Going through the  lip seal was a piece of cake. As the shaft get into the water seal it seems it does not want to come out by hand so I decide to tap it gently and all of a sudden, pling!, a piece of the seal (the one I point with the yellow pen) comes the other end but the rest of the seal stays in place. WTF. It seems the shaft has a bit bigger that the seal bore and by pushing "breaks" the seal in to piezes, one that stays in place and the other ones comes off.
I removed the shaft and pressed back the little piece that apparently it was not broken. It clicked and went back to normal.
 
1-     At this point I don’t know if I have broken the seal or not. It does not seems to me since I was able to put it back. Let say no
2-     If I make the shaft coming through gently tapping here and there,  the part of the seal in contact with the shaft will spin with the shaft. Is that ok?.
3-     Even more, in that case the spring mechanism, won’t work since the bore of the seal will be strongly connected to the shaft.
 
At this point I don’t know how to proceed after haven read lot of entries, I haven’t found out any answer to my question.
I'm a a bit lost with the different configurations, two different impeller types and also some different shafts, the ones with the male screw and the ones with the female screw. So I don't know if depending of what type of shaft I need a different seal.


Thanks you in advance for your help.




 

I think we have all been down the same road and broken the seal. 

Firstly bin the impellor you have and buy the newer version. All seal replacement kits come with the new impellor.  The manual says something similar. 

The water seal needs to be "pulled" into place slowly.  I use a collection of spacers, washers and sockets to screw it into place.  It has been a while since I overhauled one but this is the (for me) easiest way. 

If you have replaced a bearing on a shaft before then you will understand.  A socket face of the same diameter on the inside face of the seal will get it into place.  That keeps the movement force as close to possible to the shaft and places no force on the outer edge of the seal (thus breaking it).  I really need to have a photo to show this.  Forget about tapping it into place because it will not work due to the uneven force applied to the inner face. 

And I always have a spare water seal when I overhaul the oil/water pump. Simply because I forget how I did it last time and I have to break the seal to remind myself. 

The seal is ceramic, you do not "tap" it under any circumstances. Bit like taping mums fine china with a hammer (it breaks).

If you wish to use the old impeller you will need to machine 3.2mm from the boss on the vane side but it is easier to use a new pressed steel impeller.

The seal is pressed in by pressing on the outer lip till it is firmly home then the shaft is pulled through using a bolt and various spacers/sockets until the impeller can be attached and then the shaft is drawn through using the aluminium impeller boss and the impeller and the nut.
Do not press the shaft through the seal or it will destroy it.

RicK G wrote:Do not press the shaft through the seal or it will destroy it.

To supplement Tackler's and Rick's posts, here is an article—with photos—explaining one guy's method of installing these seals. Because you have a shaft with a threaded end, you'll be using a nut instead of the bolt described in the method.

Go to this site. Click on the 11-Engine diagram. Scroll down to Water Pump/Oil Pump-Oil Filter diagram 11-1974. Click on it and in the parts list is an explanation of the parts needed to rebuild this pump. The pressed steel impeller is one of those parts.

Gents thanks a lot for all the info. Now I see that there are different types of shafts, two for the cast iron impeller (male screw and female screw on on the impeller side) and another one for the pressed metal one (female screw and shorter that why it is needed an spacer). For the cast iron shaft that seal I got wont work so I will get the new impeller and the new shaft.

Thanks again to all, very useful advice.

Best regards