ID of oil cooler oil lines

[oldnortonrider]

Before I disconnect, to change, the oil lines for my oil cooler; I thought I'd like to have the new ones with correct size inside diameter, handy, to install.
It would have to be, either, 1/4", 5/16", or 3/8" .

Somebody; advise me, which size it is.

[planedick]

Line size...

If you look at the oil cooler adapter you will find a bypass valve with a hole in it of about 1/4" which is all that's needed for proper oil flow. I have just recently installed an oil cooler and I have noticed a 100% increase in oil pressure after a long hard freeway ride. It used to be I only had 20 lbs at 4000 rpm, now it is over 40 lbs. My oil cooler lines are 3/8" OD which means that the ID is just a little over 1/4"

[oldnortonrider]

Appreciate your info. Reason, I've taken a while to get back to you, is because I'm a full-time camper-outer on this fine XS11 motorcycle; -- and finally got to a "cyberstation" to check on this thread, and did see your response. My XS11 that I've had for 10 years, is an 81 Special, and had the oil cooler, from when it was new. Since, I was going to be on the run, when I did replace the lines, I wanted to make sure that I had the correct size line, before pulling one of the lines off the oil cooler. When you're traveling, living full-time on the run; - nothing comes loose to be replaced, unless you know for sure the replacement is going to be the right one.

That's most interesting, about going from 20 to 40 pounds oil pressure, when you added an oil cooler, keeping the oil thicker, keeping it that much cooler. You ought to install an oil temperature gauge. How is your oil pressure gauge mounted and installed? How'd you hook it up?