See the full article, Oil Tank Pressure, in the REF section of the Sportsterpedia.
There should not be any noticeable pressure in the oil tank.

During normal operation;
With the tank cap / dipstick removed, tank pressure is vented to atmosphere from the top of the tank.
With the tank cap / dipstick installed, tank pressure is vented to the cam chest.

During shutdown;
The oil tank vent is connected to the cam chest and the cam chest is vented out the breather valve(s) in the cam cover or heads, respectively.
So if you have pressure in your oil tank and the vent to the cam chest is not blocked then the cam chest is also pressurized.
If the cam chest is holding pressure, then your breather valve(s) can not be venting properly.

Bottom line is that if the vent system is working properly, you shouldn't have excessive pressure build up in the oil tank. ¹⁾

Oil hose sizes: ²⁾
Feed hose: 1/2 “ at tank but changes to 3/8” prior to pump.
Return hose: 3/8“ from pump to tank.
Vent hose: 1/4” from cam chest fitting to tank.

In the pics below; ³⁾

• A is the drain
• B is the feed
• C is the vent
• D is the return

94-03 Oil Tank Fittings 4)	2004-2013 Oil Tank Fittings 5)	2014 and Up Oil Tank Fittings 6)

Be careful of the feed line in the FSM diagram as it is mis-leading. ⁷⁾
Feed comes off the oil pump, under the engine, tees to the drain and up to tank.
The oil pump scavenger (return) is on the top of the oil pump at the front fitting.

On the tank;
The feed is the big nipple (1/2“) on the back side. ⁸⁾
The return is 3/8”.
The vent is 1/4“.
The return and vent lines on side of the tank facing the front of the bike.

02 oil pump fittings labeled 9)

There is a dedicated drain hose from the oil tank.
It comes out from the tank, makes a 90 degree bend to the rear and fits into a cylindrical plug welded to the underside of the battery tray.
(on the rear part of the tray, near where the batter strap is fastened) ¹¹⁾
You should see the oil feed fitting on the bottom of the tank from the chain guard side.
The drain fitting is at the bottom of the sheet metal that forms the back of the tank.

Engine oil drain hose location on a 1989 XLH 1200 12)

There is a tee in the feed hose (near the frame on the left side of the bike) and the drain hose comes off that tee.
There is a steel plug welded to the rear of the frame under the swingarm.
The drain hose fits over that plug with a worm clamp to hold it there.

Oil return and drain hose 13)	Engine oil drain hose location on a 1998 1200S 14)

• 04-05 Oil Drain Plug Mods

There is a plastic clamp (33123-04) from the bottom frame rail that has a hollow stud for the oil tank drain hose to clamp onto.
The drain hose is anchored up inside the lower rails.

Drain clamp on 04-05 models 15)		Wider view 16)

The MoCo eliminated the clamp itself and went to a solid plastic plug (33123-06). ¹⁷⁾
It has a small head that hose clamps into the drain hose and dangles between the bottom frame rails.
It just barely peeks below the frame rails. You can cut the hose a little shorter so it doesn't hang too far below the rails ¹⁸⁾

Drain plug location on an 06 883 19)

The plastic plug was updated (33123-06A).

09-up oil tank drain plug 20)