Milky oil
 

What are possible problems on the cn250 that lead to milky oil? Put fresh oil in the buggy after having the head ported and polished. Ran it for a little bit and when I checked the oil it was brownish and runny. Where could my coolant be mixing in with the oil? Anywhere besides a possible crack in the cylinder?

how about the head gasket?

Installed a new head gasket with it.

Could be a water pump seal. It has an oil seal and a coolant seal on the shaft. If that is where your leak is, check the bearings that the shaft rides on. When the bearings start to go out they let the shaft wobble which in turn takes the seals out. Not sure if this is your problem but it is a suspect area.

This is very common on dirt bike engines as well, just replaced the whole deal in my rm80. Not too involved of a repair, but the case will likely have come off to replace the seal and bearings.

This occurred after ur port and polish and you put a new head gasket. Hope you torqued your bolts tight to specs.

Head gasket is my first thought. Also did you drain the block of antifreeze when you pulled it apart?

It was like water before I pulled the head and had it ported and polished. I did not drain the coolant when I put the head back on. I ran the buggy for a little bit just to try and get it to idle after reinstalling the head. Buggy may have idled 30 to 45 minutes. Took out the dipstick to check the oil level and it ran out the top kinda milky and brownish in color. Maybe some extra in there from when I drained the oil the first time. But it somehow got mixed in there before I bought it. Head was torqued back down to specs.

You can do a leak down test to check the head gasket. Just like adjusting the valves, you'll want the piston a tdc of compression stroke. Pressurize the cylnder with a low pressure (start around 50 psi). Check for air leaking in the intake (intake valve leak), exhaust (exhaust valve leak), valve cover breather (leaking rings), and last but not least the coolant fill. If the coolant has bubbles forming that is most likely the head gasket leaking.

When pressurizing the cylnder it may try to push the piston down and open a valve. Be aware that if you are holding the crank from moving with a wrench, the piston can spin the crank and smash a finger between the wrench and part of the cage.

Learned the other day that the oil of today does not turn milky white as the oil of yesterday, when water is put into it. The oil is formulated to not float away, and this means it turns into a brown sludge that tries to trap the oil. Hard to get out, you pretty much have to wipe it all out. Plus it fills up all the oil holes and passages.