I have had this problem with my DS. I would be willing to bet it is the water pump seals. It is easy and cheap to fix. Get the two seals from the dealer, about 5 bucks, remove the three bolt that hold the water pump cover on, on the left side of engine with hose going into the top. Let the coolant drain from the removed cover. Remove the roll pin from the impeller and remove impeller. You will see a small seal, remove it. One way is to put a couple of screws into the face of the seal and use them as handles to grab with pliers and work the seal out. Once you get this seal out there is another identical seal behind it, remove it too. Clean and oil the shaft and install the new seals with the flat side towards the motor on the first one, and the flat side towards you on the last one. On the outer seal, stop when it is flush to the outside of the housing. BTW, the first seal gets driven all the way in until it bottoms out. Reinstall the impeller and roll pin. Replace cover, refill coolant, change oil and filter, and go riding.

If you can't get the seals out, no biggie, just remove the clutch cover housing and you will be able to remove the water pump shaft and the seals will be easy to remove, it's just a little more work that way.

 

When I had my lt250r I had a problem with crank seals like your water pump. We used a little bit of blue loc-tight on the outside of the seals to keep them sealed. And they still came out the same when we removed them. This might help in keeping them sealed.

 

Thanks guys i'll check that out...