Oil blowing out top of oil tank
 

My son had a problem start up on his 07 Nightster, he changed the oil, rode the bike about 50 miles and the next day when he went to go for a ride it started blowing oil up out of the top of the oil tank.
Oil level was correct according to the dipstick.

Anybody have anything like this happen before? If so, what did you find?

At least on big twins if you have a clogged breather/vent the air in the crankcase will find a way to get out. This usually occurs through the vent line to the oil tank, which can cause the dipstick to turn into a projectile and/or oil to be pushed out of the dipstick opening.

To be honest, I haven't wrenched on many sporties though so I'm not sure if they vent to the oil tank in a similar manner...

I have but it was from overfilling and Softails will do it too so if its topped off correctly maybe someone else has the real fix. hth

Sounds like it is over-filled. Did he check the oil level once he got back from his 50-mile ride. He changed the oil and checked the level while the bike was on the kickstand correct?

A Sportster oil change typically uses a little over 2 quarts added after draining. A lot of us Sporty riders just fill to the oil low line when the oil is cold. It goes about half-way up the dipstick when the oil heats up. This prevents oil blow-by from the vents into the throttle body and a chance of it venting from the oil tank. Does the oil foam?

Could be other things, but would check this out first.

My oil change procedure is (bike on kickstand). Drain oil tank, remove filter, put new filter on, pour in 2 quarts. Start bike and run a minute and check oil level. Add as necessary to get to the oil level you want (I told you where I run mine at). Ride bike around 50 miles (or until operating temp), check level one last time and add as necessary.

Yeah that. It's overfilled. If you fill a Sporty up to full on the dipstick it will blow out the top of the tank.

Appreciate the feedback guys, overfilled was my first thought as well, hopefully that is all it was, will find out for sure Saturday when we have time to fire it up again.

Any other ideas are always welcome.

You have to run the bike for a few minutes before you change the oil. particularly if it's been sitting for a long time. The oil can wet sump while sitting, and will not be drained when you empty the tank. Then after you fill it up and turn on the engine, an extra quart or two sitting in your crankcase gets pumped back into the tank and usually blows the cap off. The later models have a small vent valve on top to avoid the explosive surprise, but the oil still bleeds out from the top.

Wet sumping is fairly common for sportsters, both with the engine running, as well as sitting. Over-filling due to a cold oil change is also a common mistake, as is the resulting mess. This engine uses a dry sump oil system... oil does not belong in the crankcase as it does in a car.

Make sure you check the oil level with the engine hot, on the side stand. Most people keep their oil level between 1/4 to 1/2 way up the dipstick when checked this way. Keeping the oil level on the low side usually helps with oil blow by into the air cleaner.

I think I found the problem... Curious what caused such a huge crack, not like we live in the frozen tundra.
I am thinking...hoping...this is what caused the oil to be aerated as well.

http://www.8541hog.net/images/otcrack.jpg


http://www.8541hog.net/images/aoil.jpg