So you get to the point in a build that you need to hook up the oil lines. But which line on the engine is feed and which is return?

Some have suggested attaching hoses to the junction and leaving the ends to the tank off. Next fill both hoses with oils and kick the bike over. Oil will come out of the return line and the level in the feed line will drop. This is a messy way to determine which line is which. On the subject many of the manuals are either silent or vague about oil line positions.

Here is an easy way to remember, at least on a Triumph where the oil lines go:

Unit construction Triumph engines:

FEED IS FRONT
REAR IS RETURN
F=Front=Feed
R=Rear=Return

 

Pre-Unit is the opposite

FEED IS REAR
FRONT IS RETURN