A few weeks ago, I had typical water pump seal failure indications, mainly coolant from the weep hole, possibly a smidge of oil in the coolant.
I ordered new seals, spacer, impeller, o-rings.
On disassembling both my pump and the one from the parts bike, it turned out the one from the parts bike was unexpectedly newer ('91, though the parts bike is also '87) and had a better-looking shaft. (Though, frankly, neither shaft looked great.) So, I put the seals into the newer pump and put it on the bike.
Turns out I munged up one or both seals during installation. No shocker, as I was a bit rougher than I probably should have been with the slip-ring seal. Coolant leaks profusely; bike is back in dry-dock. Also, I'd note that since the parts bike has never been run since I've owned it, I actually have no idea as to whether its pump was actually good at the time I put it in. So it's out of the running, as far as I'm concerned. I have new seals on the way, and I plan to seat them more deliberately using a long bolt, nut, and socket as a screw press, instead of a mallet.
Upon investigation, it turns out that the K1200LT, through 2009, water/oil pumps are *identical* to the early (but not earliest) K75 pumps ('86-90). Check it out for yourself: The housing has the same part number, as do all relevant internal components. So, ever looking for a bargain, I have a very inexpensive 2004 pump on the way, along with a brand new set of seals. So here is my dilemma. Do I:
1. Bolt on the 2004 pump as-is, cross my fingers, and ride.
Advantages: least work; lowest probability (zero) of munging up another set of seals (and/or pump housing); doesn't preclude subsequent installation of new seals if indicated.
Disadvantages: Shaft condition unknown; pump's actual functional condition unknown.
2. Disassemble the 2004 pump, install new seals.
Advantages: Clear inspection of new shaft; brand new seals; relatively new part overall.
Disadvantages: More work; potential for screwing up new seals again.
3. Disassemble the 2004 pump, grab the shaft (and maybe drive gear), reassemble with new seals into original 1987 housing.
Advantages: maximizes use of parts previously working on bike, but with brand new seals and newish shaft.
Disadvantages: Gears and housing not run together; old housing might have (non-visible) wear or increased clearance where not desired; again potential for messing things up during reassembly.
I'm leaning toward #1, knowing that I can transition to #2 if necessary, at a cost of only the removal & reassembly, which has become a somewhat familiar process at this point.
