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Last weekend my buddy and I went to St. Joe State Park in St. Louis, MO. He has a 85 KX 250, after about an hour his motor, died and when he went to restart it there was no compression, we looked in the oil fill plug and found that it had water in it and was a milky grey color. The oil was changed about a month ago, there is no cracks in the motor or anything? does anyone know what caused this ??? and how water got into his motor??? it had a air box and filter all stock .

Burnt a hole in the top of the piston likely. The tranny oil is proly unrelated....

well dude i dont know what kinda riding he did does, or anything really specific, but he probably has a loose bolts, or SOME kinda crack u guys are missing for water to get inot that motor, that is the only way that the oil would change color, as far as the head goes u probably need new rings or the piston is gone.

How about this possible scenario...

Water pump seal began to leak, letting coolant into the oil. Loss of coolant into the oil led to overheating and subsequent damage to the piston and or rings.

Condensation will make your oil cloudy and also a airleak when riding through water.... There is more than one way this can happen. But tranny oil and loss of compression are usually unrelated. Except in the case of overheating, then you usually just seize....

It doesn't have a water pump, all air cooled, Also we were just racing back and forth on the flat packed sand and like 10 min of trail riding then it lost all compresion and won't start back up

first off you should change the oil more often. my guess is condesation this time of year has ruined the oil. as for the compression best way is to tear of the top end let me know what you find.!! crossing my fingers for ya but i dont think your gonna like what you'll find.

beeds3000 wrote:Last weekend my buddy and I went to St. Joe State Park in St. Louis, MO. He has a 85 KX 250, after about an hour his motor, died and when he went to restart it there was no compression, we looked in the oil fill plug and found that it had water in it and was a milky grey color. The oil was changed about a month ago, there is no cracks in the motor or anything? does anyone know what caused this ??? and how water got into his motor??? it had a air box and filter all stock .

It doesn't have a water pump, all air cooled, Also we were just racing back and forth on the flat packed sand and like 10 min of trail riding then it lost all compresion and won't start back up

Couple things. First, an 85 KX250 IS water cooled. So that causes a little confusion. But set that aside for the moment. How did it die - was he screaming along and it stopped abruptly or did it just sputter out? Has it been hard to start before this or is it a two kick and go bike? How is the maintenace? Clean filter, regular oil changes. Is the bike stored inside or out where it might get rained on.

At the very least I would be pulling the pipe off and taking a peak up in the cylinder. Check for gouges in the cylinder wall and piston, and make sure the ring(s) are intact on the piston. Pull the plug and check it's condition. These are things you can do without buying gaskets. The next step is pulling the top-end which will require $25 in gaskets and most likely a new piston and overbore. That bike is 20 years old, it's probably due!

It died when we were in top of secound going up a slight hill on the trails at St. Joe. it has always been garaged, and it has always started within the thrid kick always ran very well. pretty good maintmence, but it was his fathers bike and he doesn't know when it has had it's rings or a top end piston kit put in it. the milky grey oil was really weird since it was bright red when we started the day. your right it was water cooled my bad, but we checked the water pump and seals on that today they are all fine. so it is a mystery still how the oil got so full and grey milky looking.

Check the radiators - are they low on coolant? If the head gasket failed it could over-pressurize the cooling system and force coolant past the seals.

Did you ride through any water case deep or so? Water can get sucked up into the tranny through the breather hose.

JD wrote:Check the radiators - are they low on coolant? If the head gasket failed it could over-pressurize the cooling system and force coolant past the seals.

Did you ride through any water case deep or so? Water can get sucked up into the tranny through the breather hose.

I was just thinking that too slow in my old age lol had it happen on a cr but it also pushed water out the rad over flow