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ET: Engine (Twin) Oil Return Pipe Question


Rixon

Active Website User
VOC Member
Does anyone know the size of outlet hole in the oil return pipe fitted inside the standard Vincent oil tank?

I’m currently adapting a Norton oil tank to fit on the Norvin and it struck me that the outlet hole in the Norton return pipe may not be the same diameter.

I’m not sure how critical the size of this hole is but I may as well be safe and follow Vincent practice.
 

bmetcalf

Well Known and Active Website User
VOC Member
Away from home, so I can’t check, but I would have guessed 1/4”bsp. KTB probably has it.
 

Cyborg

Well Known and Active Website User
VOC Member
I was recently pondering the same question and ended up making the hole 1/4”.
I suppose the actual size Vincent used depends on whether it’s a B or a C. Never looked at a D. The C chain oiler setup is different, so that would come into play. This oil tank is in the tail section, so size/ length of hose could be factored in. At the end of the day, I decided it wasn’t really that critical. If for some unknown reason it wants more resistance to shove more oil to the rockers, then I can just add a restrictor to the line, but doubt that will be required.
 

Bill Thomas

Well Known and Active Website User
VOC Member
Another thing we don't think about, Till somebody asks !,
Interesting, The hole coming out the tank fitting might be small, But the metal pipe going to the pump is much bigger !, Looks to me like it takes a 7/16 " Rubber pipe .
The metal pipe that the rubber goes on, The inside is more than 3/8" but less than 7/16 ",
Must admit when I built my Special I made it bigger than 1/4", But not 7/16, That was with a home made oil tank, It's been Ok since 1975 !!.
This showing the big standard feed pipe going down between the gearbox cover and the Timing case.
 

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Rixon

Active Website User
VOC Member
Just to reiterate - I'm referring to the oil return hole located inside the oil tank. The size of the hole will surely affect the back pressure and, I assume, the oil feed to the rockers.The pipe sizes I'm ok with.
 

davidd

Well Known and Active Website User
VOC Member
3/8" sound about right for the hole that the pipe fits into. I would think that the holes in the block are drilled to 3/8", which would be perfect for slipping the return pipe into. This should allow a pipe to be inserted in the hole with somewhere near the correct ID for good oil flow. I would think that the Norton should be roughly the same size. A smaller ID does cause a slight restriction, but the oil will move faster through the smaller size tubing. The viscosity of the oil you run will also determine how much restriction there is in the system.

The locking rocker feed bolts should have no problem with an increased supply of oil passing by. It is always good to make sure that the area around the guides drains well. It does not sound like the pipes or any restriction should cause problems.

David
 

Pushrod Twin

Well Known and Active Website User
VOC Member
These 2 holes in the UFM? They would be a nominal 1/4" inside. Made from 3/8" OD tube x 1/16" wall = 1/4"ID

I couldnt get a piece of 6mm, .230" round to enter but a piece of 5mm .198" flopped around so I would suggest that the 1/4" hole had shrunk around the welded area.
 

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Chris Launders

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VOC Member
Also the standard return is much higher than an oil tank on a Norvin would be, the one on my Norvin I just put a 1/4 BSP fitting on the central oil tank and the standard pipe size into it, no restrictor.
 

Rixon

Active Website User
VOC Member
I'm using a standard Norton oil tank, not a central one.

These have an internal fixed return pipe which terminates in a flattened end. The return oil is allowed to "escape" via a hole drilled in the pipe wall.
 

Cyborg

Well Known and Active Website User
VOC Member
Siting around watching red insulating varnish dry, so made up a go/no go gauge at .250”. Just fits into the hole. C tank with the chain oiler which taps in there.

Hole in the B tank is pointing towards the side of the filler , so can’t measure accurately, but it is slightly larger and slightly oblong.

CB69739B-76C8-4246-9FFF-DC31EB9947FB.jpegB138DC58-E36B-45FF-8A75-F0B17561E887.jpeg
 
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Chris Launders

Well Known and Active Website User
VOC Member
I know you are using a Norton tank and I am familiar with them having had an atlas for the last 36 years, I was just pointing out on my Norvin I didn't bother with any sort of restriction in the tank.

I don't know the size of the hole in the Norton return pipe inside the tank off hand and I don't use mine anyway, I have a cartridge filter in the tool box and the return from that goes straight across into the oil tank, the original return pipe is blanked off.

Would all Nortons have a restriction in the return pipe, surely the ones with the pressure fed rocker set up wouldn't need one ??
 

Robert Watson

Well Known and Active Website User
VOC Member
I don't believe there is a restriction in the Vincent return line. The metal tubing bits are 5/16 tubing with the appropriate rubber hose over top and 1/4 bsp threaded fittings. the tube going from the banjo on the bottom of the oil tank to the block in the filler neck is the same 5/16 tubing with a 1/4 in ID one finds elsewhere in the oil return system......
 

timetraveller

Well Known and Active Website User
VOC Member
The answer, dear boy, is a twin start oil pump. Without a deflector to aim the issuing oil downwards inside the oil tank filler neck it will rush out so quickly that some will issue from beneath the filler cap.. No longer a drip not even a spurt, just a good flow once above a couple of thousand rpm. So much more satisfying.
 

Marcus Bowden

Well Known and Active Website User
VOC Member
Plus a Honda oil pump supplying into the gallery and cylinder lubricators blanked off, cams and followers have done over 300k so I know it works, it's just big ends I have to keep replacing. Plane bearing floating bush is what I've just put into an "A" comet with the supply pump increased to 3/16" wide delivering half as much again. On post-war Comet's, I'm thinking of increasing the size of the Honda pump and directing it all into the filter housing so it gives a constant supply with mechanical seal to the main shaft possibly restricted as I like to see at least 8 to 10 psi to cams, normally running at about 1 Bar. As for modifying a twin to plain bearings is yet to be thought about. Never have I replaced a ships B/E bearing and they do hundred's of thousands of "hours" lasting 25 to 30 years that I've sailed on!
Roller B/E's take little oil but the contact surface is bearly measurable.
 

Rixon

Active Website User
VOC Member
Just measured the outlet hole (oil return line) in the Norton oil tank I'm using and it's 1/8" diameter. Based on the feedback I'll be modifying it to 1/4". Thanks for all the useful info.
 

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