Problem - Crankcase filling with water

[MNellis]

I just got my '00 426 back together after a complete rebuild and started it up without much problem. I forgot to put the bolt on the cam chain tensioner and immediately something squirting out the hole. I also noticed that what was squirting out was not oil but water. I shut it down promptly but not I'm trying to figure out why the crankcase filled with water. Apparently my failure to install the bolt was a blessing in disquise. I drained the oil and it was full of water and the oil was milky. The engine didn't run for more than about 20 seconds.

I took apart the right case and the 'O' on the water pipe is in place but it looks fairly thin. I ordered a new 'O' ring to verify I have the correct one in place so it'll be about a week before it gets here. I haven't taken the cylinder off yet to check that the other 'O' ring is in place but will probably do that tonight.

http://www.bmnellis.com/images/yz426/waterpump-parts.jpg

Are there any other 'O' rings I could have missed or can someone think of another reason the water would RAPIDLY fill the crank case?

Thanks

[02YZ426]

Did you check the water pump seal itself? Maybe thats leaking

[MNellis]

Yes, that all looks fine.

[grayracer513]

Head gasket backwards?

That's pretty wild. The cooling system only holds about a quart.

Got a little brother, maybe?

[MNellis]

Head gasket backwards?

That's pretty wild. The cooling system only holds about a quart.

Got a little brother, maybe?

Yea, but he died last year and he was 47 so I doubt he'd play with my motorcycle.

I think it was like 1.2qts

I thought about the head gasket backwards thing but I don't think that's possible. The dowl pins should keep that from happening but here is a clue. There are a couple of "ears" of the head gasket that stick out from the back of the head? Is that correct? If not then maybe it is on backward. ?

[MNellis]

you know mr. GrayRacer, you might be on to something. I wouldn't have thought I would make that kind of error but I just went out and looked at the head gasket area a little closer and there are some pieces of gasket sticking out that don't seem to make sense.

I'll pull the cylinder off next week when I get back from a 2 day track event at Barber Motor sports.

Thanks for the tip.

[sirthumpalot]

Get yourself a cooling system pressure tester. When you have it back together, plug it up and if the cooling system won't hold pressure then you'll know there's a problem right away, and before you get to the track! Let us know what you find, hopefully it's the gasget as mentioned above.

[biznet1]

you know mr. GrayRacer, you might be on to something. I wouldn't have thought I would make that kind of error but I just went out and looked at the head gasket area a little closer and there are some pieces of gasket sticking out that don't seem to make sense.

I'll pull the cylinder off next week when I get back from a 2 day track event at Barber Motor sports.

Thanks for the tip.

The gasket I used (moose) does have a couple of little ears as you describe.

[MNellis]

I finally got off my ass and found the reason my bike was pouring water in the oil. After ordering new O rings for all the water tubes that enter the engine as well as a new head gasket I started putting the engine back together. I was putting the cylinder on and was having problems getting the cam chain into position agains the front guide. I got a flashlight out to see what the problem was and noticed something was down there. I fished it out with a magnet and found my water problem.

As with most things it's usually "operator error" and this was not exception. When I was taking the engine apart for a total rebuild I removed the plug in the head that's right next to the spark plug...just to see what it did. I thought I had put it back in but I must not have tightened it. Well, when this plug falls out then all the water that it's holding back goes straight into the crankcase.

Anyway, the bike is running great and the 450 cam mod works like a charm.

Now it's time for this old guy to relearn how to ride an MX bike after almost 30 years.

[grayracer513]

When I was taking the engine apart for a total rebuild I removed the plug in the head that's right next to the spark plug...just to see what it did. I thought I had put it back in but I must not have tightened it. Well, when this plug falls out then all the water that it's holding back goes straight into the crankcase.

Well, a couple of people have asked what that plug is for. Now we know for sure. There's an upside to everything....Almost.