What causes this? Is it a leak in the water pump or a leak in the crankshaft seals or something else?

Irrelevant really as the bike I'm doing is having a full rebuild, but I'm just interested!

 

counter balance seal is gone letting in water of antifreeze from the coolant system. full rebuild should take care of it. maybe some others will chime in on some recomendations. it may just need to be changed.

steve

 

A seal change is in order. I'm not sure on what all is involved but I don't think it's too hard. Good thing you caught it early cause a counterbalancer bearing lockup is not good. Big time rebuild.

 

The quad is still currently in use, so we'll be changing the counterbalance oil after every ride to make sure it's always tip-top until I can strip it down. It's a friend's quad and he needs it for working on his farm.

I've devised a quick way of getting the dipstick out of such a fiddly place - just use a piece of rubber tubing slid over the top of it!

I use a funnel with a tube attached to get the oil in there... whole process takes 5 minutes, as I've recommended that he pulls the drain plug every time he puts it away at the end of the day, so it's all out when he comes to it next time. (It's used about once every four days, so it's not a major problem!)