To run with this mix of distilled water and antifreze would not be a problem, but a good idear if you can is to flush the system every 6 months and then come winter top up with 25% more antifreeze. This has worked for me.
I have met a lot of travellers on the BMW GS650 who have had water pump seals go, and i have met quite a few who have had no problems at all and they recomend to flush the system to clear it of any corrosion and then refill with new coolant. Well i hope this is of some help Skip
Do the best you can with what you have,
A stranger in a strange land now heading North South East West to.....