Coolant in the oil.

Hey guys I went out on my first ride on my new yz125 yesterday and everything went fine on that but I started to notice an odd sound from my BROTHERS yz85, its almost like a low pitched spinning sound from the bottom end. Our friends who we were with drained the oil on the side of the track and it was a very light grey color. Where do I start with this? Only place I can think of would be the gasket between the cylinder and the case, and could the bottom end be bad? I think I'll go ahead and pull the cylinder off and inspect the gasket but I wouldn't think the coolant would make any different sound.

Before you get too into the teardown, has the bike been through any deep water crossings or possibly dumped in a creek or something similar?


About the only way for the coolant to get into the cases would be from the waterpump seals.  That is the first place I would look for a potential leak if the bike had not been dumped in a creek.


The waterjacket in the cylinder and head are closed systems and never get near the cases (unless someone did some really bad things with a dremel).

Like the person above said, if you haven't ridden through water first thing I'd check is the waterpump seal. Easy change, and fairly cheap. just don't pull the kickstart gear out like I did, ha

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