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2004 Sportsman 700 EFI. Have only had the bike for about a year. First time I changed the oil nothing stood out to me with it being milky. Went on a hunting trip where I had some issues. Had the bike idling while getting ready and it started to sputter, I got on and gave it throttle where she died. After a while we found milky gas in the fuel tank. drained the tank flushed with clean gas and flushed the schrader. Pulled the plugs and let them dry a bit. Put everything back together and it ran great. I only ran it a short time up the hill and back down and our trip was over. Brought it home and it sat for about a month before I got to change the oil, just routine maintenance. Thats when I noticed the milky oil. I ran the bike for about 20 minutes after oil change just to plow my drive. checked the oil and it was a little milky again. To my fault I haven't really kept up on checking the coolant levels (now I will). I'm wondering if having that much watery fuel could cause an issue with my oil being milky? I will watch my coolant closely going forward but I also don't want to run it if it bleeding coolant and cause more issues. Could it possibly be just condensation? its kept in a non insulated garage with no heat or a/c. I live in northern Illinois where we have had a mild wet winter so far but I also have not been riding it for more than 5-10 minutes at a time. When on the hunting trip it rained a lot over the course of a week where it sat outside but I was not riding it in the rain and did not go in any water above the bottom of the rim. The water in the fuel is another issue, I'm not sure how it got in there.
 

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Does this bike have a remote oil reservoir? My 06 Sportsman 500 has the reservoir and every spring after it sits all winter (not my main bike anymore) the oil is milky. My main mechanic told me it due to condensation and to just make sure I drain it and not run it if I can help it with that oil in it. I do this every spring now and haven’t had an issue with it causing any problems.


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It sounds to me as if you're not running the engine long enough to get it up to operating temperature to get rid of some of that moisture. 10 minutes of running is not getting the operating temperature to where it needs to be to burn off that moisture. Fill the gas tank and send it!!
 

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Leak down or compression test will tell you if your head or head gasket are leaking.
 

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Leak down or compression test will tell you if your head or head gasket are leaking.
Leak down will tell you how much compression is leaking and if it it leaking great enough you will be able to determine where the compression is going, but about the only way to get coolant into the oil is from the water pump and then it has to be a failure of two seals. Most moisture in the engine oil is from condensation and engines started at temperatures below 40* F and not run for at least an hour will have more condensation than engines not started at all.

The condensation created by one cold start requires the engine to be run perhaps as long as one hour to evaporate the condensation from the oil. The temperature of the oil and metal parts of the engine does not play as big a role in removing moisture as the ventilation of the crankcase and the time of operation of the engine.

Water will evaporate at any temperature, it just evaporates faster as temperature rises and the relative humidity of the air above the water decreases. Winter air is relatively dry compared to summer air - if the outside air can be drawn through the crankcase as the engine is operated, the moisture will be removed faster. Most of today's engines have minimal ventilation due to environmental concerns. They rely on combustion leakage into the crankcase to be drawn into the air filter and recirculated to remove oil vapor, water vapor and other combustion byproducts. The process of combustion creates a certain amount of water vapor which appears as steam when the air temperature is cool enough to condense the vapor as it exits the exhaust pipe.

The combustion gases that leak past the rings contain water vapor which condenses on the cold metal parts of the engine. If you heat a piece of aluminum with a flame, moisture from the flame will condense on the surface before it heats sufficiently to cease the condensation from the flame. The moisture in combustion gas condenses on the colder metal parts the same as the moisture in the atmospheric air condenses on cold metal parts as the air temperature rises.

If you are going to start your engine, run it long enough to heat it and the oil sufficiently to vaporize all the condensation. Idling won't do it. The oil is heated by the metal parts as well as being squeezed through fractional spaces. Inside an engine, oil is heated by squeezing it between the camshaft and the cam journals, it is heated when squeezed between the cam lobe and the rocker arm pad and without pointing out all the places in an engine where oil is heated, the biggest oil heating generator is the oil pump. At idle the oil pressure is low and heating is minimized. Running at a high constant speed heats the oil the most. That's why sport vehicles may have an oil cooler while utility vehicles may not have an oil cooler and most race engines will have an oil cooler.
 
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