Oil lines on the mongrel

[tompkins]

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!

 

[Fast Eddie]

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.

 

[tompkins]

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.

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?

 

[Fast Eddie]

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.

 

[tompkins]

If anybody ends up searching in the future,

Feed from tank 5/16
Return to tank 5/16
Scavenge feed line to head 3/16

If equipping a Norton filter setup, input and output both 3/8, so reducers

All measured with digital calipers- no more guess work!

Long and short seems to be, if you’re gonna add a filter, probably time and almost money ahead to just buy one of the nice kits available from map or legend or any other. Lotsa trips to the hardware store inventing brackets and elbows and reducers! But the peace of mind from all new lines and a filter- priceless!

 

[tompkins]

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A couple-a pics of the old beastie if anybodys interested

 

[Triton Thrasher]

Triumph gave up on full pressure feed to the rockers in the 1940s.

The restriction in the return line, to divert scavenged oil to the rockers, is a 7/32” hole. People experiment with smaller holes.

The same system of tapping oil from the return line shows up on BSAs and Nortons.

 

[tompkins]

Triumph gave up on full pressure feed to the rockers in the 1940s.

The restriction in the return line, to divert scavenged oil to the rockers, is a 7/32” hole. People experiment with smaller holes.

The same system of tapping oil from the return line shows up on BSAs and Nortons.

This is interesting! If it works, why not, just seems like a strange work around with pressure feed so close- any idea why they gave up on it in the 40’s? Musta been starving the bottom end or too much oil in the head

 

[Triton Thrasher]

any idea why they gave up on it in the 40’s? Musta been starving the bottom end or too much oil in the head

I can think of possibilities.

A long pipe and it’s unions, full of hot oil at 50 psi, are a liability. Any fracture in the metal tubing commonly used back then is a roadside breakdown and possibly a mechanical disaster. Even a tiny leak can spray hot oil in an impressive fashion.

They gave up on oil pressure gauges about the same time.

They may have found it difficult to get consistent flow of both hot and cold oil. 1940s oil wasn’t multigrade; it was very thick when cold and very thin when hot. That’s a bit of a guess by me.

Norton changed their twins to full pressure valve gear feed in the early or mid 1960s, by which time suitable flexible pipe was commonplace. Norton doubled their oil pump speed (not so easy for Triumph to do) and restricted flow through the rocker shafts.

 

[tompkins]

I can think of possibilities.

A long pipe and it’s unions, full of hot oil at 50 psi, are a liability. Any fracture in the metal tubing commonly used back then is a roadside breakdown and possibly a mechanical disaster. Even a tiny leak can spray hot oil in an impressive fashion.

They gave up on oil pressure gauges about the same time.

They may have found it difficult to get consistent flow of both hot and cold oil. 1940s oil wasn’t multigrade; it was very thick when cold and very thin when hot. That’s a bit of a guess by me.

Norton changed their twins to full pressure valve gear feed in the early or mid 1960s, by which time suitable flexible pipe was commonplace. Norton doubled their oil pump speed (not so easy for Triumph to do) and restricted flow through the rocker shafts.

this makes total sense- if you pull off the back side it minimizes chance for catastrophic failure!