A: Oil Pipework Series D oil tank

[Gary Gittleson]

Does anyone have a picture of the insides of an Open Series D oil tank? I'd like to know what the chain oiler and return lines look like. I'm trying to figure out how to stop oil from coming out the breather hole in the cap with the chain oiler plugged off.

 

[davidd]

Gary,

The oil pipe work inside the D oil tank should be similar to the C UFM in concept:

If you peer into the oil filler hole you should see the oil block that is brazed in and it should have a screw in the top for adjusting the oil flow to the chain oiler. This is where you problem lies. When your engine is running there is a small hole in the side of that block. The block being attached to the oil return line, the oil coming out of the block is your true oil return oil stream.

Unfortunately, the oil return stream of oil, being so high up in the tank and so near your vented oil cap I suspect it is coming out of the oil vent hole or around the old oil cap gasket, or both. This is not unusual. On the Series C bikes it was not unusual to find when racing your Vin that putting your chin near the tank as you headed down the straight which is good for stream lining, would get you a squirt of oil on your face shield.

I originally made a disc from a beer can with a hole near the edge that I could install under the screw in the block. This worked fine until someone helping me in the pits dropped the disc into the tank. I simply made another, but months later when I removed the UFM I made an "idiot proof" one shaped like a carb slide and attached to the cap. This was perfect. Unfortunately, again, when I went to make another I realized that these brazed in blocks were not uniform in their brazed in positions and I found there was little room to do it on the current race bike. The cap was quite close to the block.

This slide is just diverting the oil away from the oil cap. You don't want whatever diverter you come up with to be air tight as well because the cap needs to vent the air in the tank.

Check the gasket and you may want to try your skills with the beer can for a test...of your mechanical skills, that is.

David

 

[Bill Thomas]

Also if you have a twin start oil pump, it makes it worse. Cheers Bill.

 

[greg brillus]

The actual outlet in the oil tank to the chain oiler line is a hole on the right side of that steel junction block mounted in the oil tank. The oil fed to it is via the small adjuster in the oil return line on that same block. If you carefully tighten that adjuster this should block off any feed oil to the chain oil line, save some oil mist caused by rapid returning oil in this area when the engine is at an elevated speed. This chain oil line is the actual vent for the oil tank not the pin hole in the cap. My advice is to wind that adjuster fully down and open the line back up to vent how it should, perhaps re-rout the line with some flexible pipe rearward to the back wheel axle. A lot of Vincent owners feel that the pin hole in the tank cap is plenty enough to vent the tank, but I beg to differ..........If a simple pin hole is all that was needed, then why didn't Triumph, Norton, BSA do the same rather that have and actual vent in the roof of their oil tanks. Cheers...............Greg.

 

[Simon Dinsdale]

Greg. Don't forget that Triumph, Norton's etc had geared pumps providing high pressure oil to plain bearing big ends etc and so the returning oil was at such a pressure the oil tank could suffer breathing problems. On a Vincent the oil circulates at such a low pressure it doesn't pressurise the tank much. I have done over 50,000 miles with the chain oiler completely blanked off and have never seen oil blowing out the small breather hole in the cap.

 

[greg brillus]

I know of several people including my self who have at elevated speeds had oil spewing from the tank cap. Not all Vincent owners with Girdraulics have had tank slappers either, but I see logic in how the tank breathing works. The oil system may not be high pressure or flow but it does scavenge at approximately twice the volume as what it delivers. It is my belief that at elevated engine speeds that the small hole in the tank cap would struggle to flow enough to compensate this difference in volume. I tend to look at why designers do something and then reason why we should change it ........I prefer to leave my tank breather/chain oiler open and run to the back axle. Perhaps some just don't ride fast enough for it to be an issue................

 

[davidd]

Greg is certainly correct about the chain oiler being a vent on the Series B UFM's as there was no metering screw. The same could be applied to the Series C UFM's in general. I was under the impression that with the metering screw fully seated there would be no flow of oil or air down the tube resulting in the plug at the rear being redundant. For this reason I did not view the chain oiler as a vent for the oil tank on the Series C RFM's.

I have never run an chain oiler and always blocked off the the feed at the rear of the UFM and I have not to date needed any more than the oil cap to vent the oil tank. If I did have an oil tank breathing problem I would consider using the chain oiler tube as a vent. The cap has always been a sufficient vent.

I do like the Egli oil view tube. It is a much better way to monitor the oil flow. I think the Vincent block that is brazed in the filler neck should have had a down tube attached. Shooting the oil out to smash into the other side of the filler neck right next to any vent hole is an invitation for a mess. Most owners do not rev to 7000, but if you pulled of my cap at 7000 rpm you would have an oilnado even with the modest pressure Vincent oil pump. I think the racers were prone to this.

I must admit that I usually enlarge the vent holes in the caps a drill size or so bigger.

The smaller sketch of the tubes below and to the right of the drawing is drawn as a view from the rear of the RFM, so the feed pipe to the engine is on the left, the chain oiler on the right and the return tube is further up front in the middle of the tank.

David

 

[Gary Gittleson]

Does anyone here have an opinion on this mod?
http://www.voc.uk.com/net/docs/4.1/4.1-571-32.pdf

I'm thinking of getting another D-style ET24/6 and after modifying the return block, piping the disabled chain oiler to that. I say "another" because I already have one over the inlet valve on the front cylinder, connected to a hose with a one-way valve and an extension out the back past the rear axle.
Cheers,
Gary

 

[greg brillus]

I have the pipe coming off the T 29 fitting and joined via a "T" piece into the breather line which is a "D" type above the front exhaust valve, these two then vent to the back axle using a length of 3/8 " bore flexible hose.

 

[vibrac]

I think logically Greg is right about the breathing aspect of the chain oil pipe but practically the only time I have had trouble with the racing Comet was when we filled the tank too high I always raced with the oil level just over the platform because the races were short remember however I used R and of course that's a well behaved oil that knows it's place