• Routing Oil Lines for an Oil Cooler
• Running Copper Oil Lines

Click on a pic to enlarge:

The OD of the oil & vent lines is as important as the ID. ¹⁾
If you buy automotive lines that are larger OD, they will be difficult to run in the limited space and easy to kink.
Oil lines for 59 and up:
Feed and Return: 3/8“ ID X 5/8” OD reinforced rubber.
Vent: 1/4“ ID, 1/2” OD reinforced rubber.

The stock lunch box tanks have the vent and return lines on the top of the tank (and feed on the bottom). ²⁾
Return (L), Vent (R)

This tank is pretty straight forward. ³⁾
Top (2) fittings are vent and fill.
Bottom fitting is supply to the engine.
It also has no drain fitting.

On this one (on a 74 XLH), the vent is higher than the feed and return lines. ⁴⁾

The oil filter (HD 63782-80T) is the small one that is usually used on custom bikes. Chrome or black can be found. ⁵⁾

It is also commonly known that the more oil you hold, the more motor heat can be transferred to dissipate that heat.
Race bikes have huge oil tanks for that reason. ⁶⁾
If you go the filter route, be sure to purge the lines by bleeding the pump front nipple first while running.
Then take the return line and place it into a pail before you connect to the barb tank fitting so you assure a complete circle has been made.

Oil Line Routing 7)

74 XLH Oil Filter Plumbing 8)

Early Sportsters had the lines route to the top of the case. ⁹⁾
Later the MoCo routed a line directly to the back of the oil pump.

There is a transmission vent on top of the case in the area near the starter solenoid. ¹⁰⁾
This one should just vent to atmosphere, either up attached to the frame, or down aimed to ground.

Oil line connections on a 67 model 11) 1- Return to tank, 2- Supply to motor, 3- Vent hose 12)

Oil lines on a 74 XLH 13)	Oil fittings on a 75 custom 14)	Oil lines on a 75 XLH 15)