Oil lines on the mongrel

Howdy British afficianados! Got the 650 twin project rolling under its own power, now it’s time to try to keep all the fluids where they go… same bike from ‘vestigial parts’, tr6c frame, t120r (1970) motor, everything else from various Brit bikes of various vintage! She’s a leaker, but not from the motor so far! I think all the oil lines that were on it are probably the wrong size, so now I’m going point to point, tightening clamps trying to stem the flow. Question-

#1- what size feed / return? 1970 motor, standard front feed rear return arrangement, heard some say theyre the same, others say one is 3/8 other is 5/16

#2- what’s the solution for the rocker box line? The tank I have is not the standard triumph tank (I think it’s maybe 50s BSA?) but the hookups look functionble- big screw in basket filter on the feed out the bottom, return is big on the bottom, small on the top for the rocker feed. It’s like maybe 1/8 for the rocker feed outta the tank - what’s the standard size? The rocker feed pipe (with the banjo fittings) looks bigger, like maybe 1/4 or more?

Everything is working fine, trouble is just getting everything tight enough to stop up the leaks. Thanks!

On Triumphs the rockers are fed off of a T in the return line. The return pipe inside the oil tank is reduced in order to create pressure in the return line, and this pressure ensures the rockers get a (barely) adequate oil feed.

I don’t know anything about BSA oil tanks, you need to check it has the same arrangement, if there is no restriction then your rockers will get insufficient oil.

Fast Eddie said:

On Triumphs the rockers are fed off of a T in the return line. The return pipe inside the oil tank is reduced in order to create pressure in the return line, and this pressure ensures the rockers get a (barely) adequate oil feedj

I don’t know anything about BSA oil tanks, you need to check it has the same arrangement, if there is no restriction then your rockers will get insufficient oil.

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yeah I'm learning all about oil routing- do you (or anybody) know why they pull oil for the head off the scavenge side on triumphs? Seems weird and unnecessary to me. I'm no engineer (obviously) but why not just put a banjo on the oil pressure light switch thingamabob in the front of the case or somewhere else? Seems like lotsa potential places to tap into the pressure feed. Too much oil or something?

Why did they do it? Why not?? It worked for hundreds of thousands of bikes and untold millions of miles.

Yes, some people do exactly that pressure feed mod on Triumphs, even top race builders like Monty and Ward, Dave Degens, and others. However, I believe Monty and Ward used to upgrade the oil pump.

Arguments for are more oil flow and pressure to the top end. Cooler oil. Cooler head. Etc.

Arguments against are that the top end just doesn’t need it and you’re robbing pressure from the bottom end which does.

If you upgrade the oil pump to a Morgo rotary pump which has WAY more flow and pressure than needed, then the ‘robbing of the bottom end pressure’ argument would be null and void.