Hi Again! 
            Next job i was planning is replacing the oil/water pump on my 1990 K100. So just wanted to know how difficult is this? i was planning on getting a reconditioned one from Motor Works. Any tips how to guides out their? info on Gaskets ect? anything else worth doing on the cooling system while i am in their? Recommendations on coolant? Thanks in advance K.

Look on YouTube. There's a K1100LT water pump video.

Any coolant should be fine.

It is a very simple job to replace the pump on a K. Empty the coolant by pulling the hose off the pump, remove the front cover and sensor wire connector, remove main body bolts and pull the pump off.
Replace in reverse using Permatex Ultra blue or black RTV sealer. I tried other sealers like hylomar etc but it always leaked. Flush the coolant from the old system and fill with a bike specific coolant (pink) for alloiy engine block. Takes approx 3 litres.
If you want a cheaper option then rebuild your own pump with new seals if the gear shaft is in good shape. 
Did the oil get contaminated with coolant? If so do an engine flush as I did with 1.75 litres 20w50 and 2 litres of Dex ATF fluid mix. Put bike on stand and run at 3000 rpm for 20 mins then drain, fit a new filter and refill with fresh 20w50. You’ll be amazed how clean the oil is now! 
I also pulled the sump off of mine which is also just taking a few bolts off. Very easy job.

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Thanks for that nobbylon I will flush it as well!