• 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.

There are generally 4 holes on all early style oil tanks. ²⁾
Two near the bottom of the tank and two near the top.
The feed line will be near the bottom and the return line near the top.
These two lines will be bigger than the other two.
The smaller line at the bottom is the chain oiler (often not used and blocked off or just turned off). The smaller line at the top is the vent for the tank.
(on early engines it runs to the top of the case just behind the rear cylinder)
There are internal drilling to route the vent into the cam chest (which vents to atmosphere).
On later engines it runs down to the cam cover which has a 90° fitting to accommodate it.
Horseshoe tank: (L) Stock tank ³⁾, (R) Generic XLCH oil tank sketch ⁴⁾

Aftermarket horseshoe tank (no drain): ^{5) 6)}

The stock lunch box tanks have the vent and return lines on the top of the tank (and feed on the bottom). ⁷⁾
Return (L), Vent (R)

This tank is pretty straight forward. ⁸⁾
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. ⁹⁾

The oil filter (HD 63782-80T) is the small one that is usually used on custom bikes. Chrome or black can be found. ¹⁰⁾

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. ¹¹⁾
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 12)

74 XLH Oil Filter Plumbing 13)

Early Sportsters had the lines route to the top of the case. ¹⁴⁾
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. ¹⁵⁾
This one should just vent to atmosphere, either up attached to the frame, or down aimed to ground.

Oil line connections on a 61 XLCH 16) Fittings (L) Return, (R) Feed, (hole) Vent	Oil line connections on a 67 XLH 17) 1- Return to tank, 2- Supply to motor, 3- Vent hose 18)	Oil line connections on a 68 XLCH 19)

Oil lines on a 74 XLH 20)	Oil fittings on a 75 custom 21)	Oil lines on a 75 XLH 22)