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A: Oil Pipework Return Oil Pressure High?

John Fewster

Website User
VOC Member
Blowing ferrule joint with return pipe A58. Problem came suddenly. I started bike after few weeks off and noticed the oil return pipe A58 along with rubber section to rear rocker feed was pulsating like a vein about to burst. Never noticed this before. It settled down after a few minutes and I made short test drive. When I restarted, the pulsations pushed the rubber section clean off top of return pipe A58 and the junction with A68 to rear rocker feed banjo. Stopped immediately since oil was peeing out. I have since blown out with airline (no blockages found) and removed all rocker feed banjos and re fitted all new washers etc. Very easy to blow through pipe to tank so positively no blocks. Re fitted all the rubber sections of hose (slightly longer bits) all de-greased and hylomared. Standard push fit (not crimped) ferrules as have been in place for years no problem. Started up. Oil pumping through to tank return straight away no problem... BUT return pipe still 'throbbing' and after couple of seconds oil seeping copiously from ferrule joint top of A58 return pipe!!! Help! - John Fewster
 

Comet Rider

Well Known and Active Website User
VOC Member
John,
Depending upon the age of the rubber pipe, it maybe breaking down internally, especially if you have changed oil supplier recently.
If you can, as an experiment try using a different length of pipe and see what happens

Best of luck
 

b'knighted

Well Known and Active Website User
VOC Member
I'd undo the banjo connection to the underside of the oil tank. Check that the holes in the banjo bolt are clear.
Many years ago I had a Comet breather spindle break up. A bit of the debris got under the steady plate and scraped the side of the aluminium large idler. This manufactured a Brillo pad which grew in the rubber pipe but caught on the top copper pipe pushing the rubber off it. The first I knew was when my warm boot slid off the brake pedal.
 
Last edited:

Bill Thomas

Well Known and Active Website User
VOC Member
John, Are your pipes Chromed, They said years ago that might not be a good idea.
Too Slippy, Although mine are and are OK.
Also My Comet has a longer bit of rubber pipe than it should and also has throbbing,
But has done it for years and no problem.
Cheers Bill.
 

Robert Watson

Well Known and Active Website User
VOC Member
We had a recently assembled engine that did exactly that. Whilst sitting at some point with the cylinders off a mouse had built a nest in the cases. sometime much later after startup the return oil line blew at the banjo on the return under the tank. After considerable examination and retrieving large amounts of fuzz from all the return lines and fishing a couple of big wads from the cases, and checking all the return lines were clear we got back to normal. Fortunately non made it to the pressure side of the system!

Don't tell that the little wires in the rocker feed bolts stop the oil flow. They all had wispy bits of mouse nest down into the bottom of those bolts. Pulled the rockers out but found no wispy bits past there. That engine only had about 10 miles on it at that Point!
 

John Fewster

Website User
VOC Member
Thanks folks for comments so far. All rocker gear clear. Can easily blow through from A58 to cylinder head return in oil tank, so I have no idea where any back pressure could come from. I do have chromed oil pipes which could well be more slippy than optimum... however no problems since 1974!.. also I checked... no rodents... so I cant understand why suddenly now... my next move is to clamp each end of the hose down tight with crappy jubilee clips... if I don't get an oil gush from elsewhere I will do a bit of ferrule crimping!
 

Chris Launders

Well Known and Active Website User
VOC Member
Don't forget that it being easy to blow through doesn't mean it will flow oil easily, there is a SLIGHT difference in viscosity between air and oil, I would take everything off and try to look or poke something through everything.
 

Bill Thomas

Well Known and Active Website User
VOC Member
Looks like I will have to carry a bit of rubber oil pipe,
Something else to worry about !,
Need a bigger tank bag :D.
The Vincent oil pump does tend to work in fits and farts as normal,
There is never a stream of oil.
My oil returns to the tank OK, As I have said before, I check it before every ride.
 

davidd

Well Known and Active Website User
VOC Member
Thanks folks for comments so far. All rocker gear clear. Can easily blow through from A58 to cylinder head return in oil tank, so I have no idea where any back pressure could come from. I do have chromed oil pipes which could well be more slippy than optimum... however no problems since 1974!.. also I checked... no rodents... so I cant understand why suddenly now... my next move is to clamp each end of the hose down tight with crappy jubilee clips... if I don't get an oil gush from elsewhere I will do a bit of ferrule crimping!

John,

I would guess that there was a restriction in the steel pipe that runs from the return up to the filler neck. I had the pulsating when a nylon ATD tooth came off and worked its way to the return. It was too large to go inside the pipe, but a bit of debris or gasket goo could have done so.

It sounds like it has been cleared, which is good. It is a shame that Vincent did not filter the oil return as it pumps a lot of debris back into the oil tank.

Oil Filters.jpg

I did this on the racer, but I had the room under the tank. The return line ran up to the filter and then the filtered oil came down to the return on the UFM. This has been done on some street bikes by mounting the filter on the RFM pivot (bottom side). It was done on a few Series A bikes for cooling, not filtering, but the filtering cannot hurt.

David
 

John Fewster

Website User
VOC Member
Think solution found. I have chromed oil pipes and also double capacity pump worm. Pressure, though low, is slightly higher on startup and just enough to blow off the un-crimped rubber section. Once it first happened I cleaned, degreased and hylomared but it still throbbed and popped off after couple seconds running. I just now cleaned off again and stuck on 2x unsightly jubilee clips... and problem solved! No idea why it was OK for over 40 years then suddenly popped? May have been temporary blockage in rocker returns but I found no evidence. Did see evidence of red Hermetite on the pipes before cleaning and refitting. This stuff sets bit firmer than Hylomar so probably held seal for longer on the slippery chrome tube. I will eventually remove the jubilee clips, roughen the chrome under the rubber pipe, revert to Hermetite and do proper s/s ferrules with crimping on just these 2 joints.
 

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