Air Pressure Release

[Soupy1957]

I don't know if it's only true of Harleys, but........

I gave my Road Glide Ultra an oil and filter change yesterday. After adding the 3 Qts., as instructed by the owners manual, I put the filler cap back in place and tightened it down and started the bike.

After five minutes I shut it off and removed the filler cap so that I could check the level and see if I needed to add any more oil.

When I got all the threads of the filler cap out I heard a pressurized air release coming from the oil tank. I didn't expect that. Anyone know why that occurred?

 

[joel]

Not sure if it is normal.
I did see when a guy started his Sporty, the fill cap blew off and the oil hit the under side of the roof above the gas pumps.
He may have had a much bigger problem than a little pressure build up. But it was funny at the time.

 

[Soupy1957]

When the oil is drained out, it introduces air into the chamber. That "air" gets pushed out when I refill the chamber, but why a pressure-push (fart) of air after the initial running, I dunno?!

How about it "Service Tech's" who are in here reading this........is the oil in a vacuum system, causing the air release I experienced??

I was watching a video a few minutes ago about engine crank case pressure, and I don't know if this is related or not but here's the link:

 

[fin_676]

Harley Davidson motorcycles use a dry sump system
the oil in the oil tank is the oil pulled in by the oil pump to lubricate the engine the oil collected in the engine sump is pushed back to the oil tank by the oil pump
when the engine stops the oil pump stops the oil that is in the engine at the time drains into the engine sump where it builds up
once the engine is started the pump gathers all the sump oil and pushes it back to the oil tank this in some circumstances can create a wee bit of pressure build up in the oil tank
Prior to draining the engine oil the bike should be run till warm to ensure their is no excess oil in the sump
Add the same amount of oil as drained check there is a presence of oil on the dip stick start and run bike till engine is fully warmed up then check the oil level and top up as necessary
Dry sump systems are different to work with from wet sump systems follow the correct procedure and you will have the correct amount of oil and no pressure build up

Brian