• Welcome to the website of the Vincent H.R.D. Owners Club.

    Should you have any questions relating to the Vincent H.R.D. Owners Club, or Vincent H.R.D. motorcycles in general, please contact Graham Smith, Hon. Editor and Webmaster by calling 07977 001 025 or please CLICK HERE.

    You are unrecognised, and therefore, only have VERY restricted access to the many features of this website.

    If you have previously registered to use this forum, you should log in now. CLICK HERE.

    If you have never registered to use this website before, please CLICK HERE.

A: Oil Pipework Series D oil tank


Gary Gittleson

Well Known and Active Website User
VOC Member
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

Well Known and Active Website User
VOC Member
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.

oil lines schematic.jpg

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I originally made a disc from a beer can with a hole near the edge that I could install under the screw in the block.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.

OilSplashGuard02.JPG
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
 

greg brillus

Well Known and Active Website User
VOC Member
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.
 

vin998

Well Known and Active Website User
VOC Member
VOC Forum Moderator
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

Well Known and Active Website User
VOC Member
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

Well Known and Active Website User
VOC Member
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

Well Known and Active Website User
VOC Member
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

Well Known and Active Website User
VOC Member
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

Well Known and Active Website User
VOC Member
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:)
 

davidd

Well Known and Active Website User
VOC Member
Greg is correct that the C chain oiler is a moonlighting as a breather, but not by logic. It is because there is another hole in the block that is not visible, but shown in the riders handbook!

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.
Gary,

I am not sure I understand why you want to add another breather, but I know multiple breathers are popular. I have never had any problems with any breather on a Vincent including the caps. You do have to check the holes in the caps to make sure they are not plugged up.

Unlike the C, the D has a number 70 Amal jet in the chain oiler, but also uses the standard metering screw used on the C, which is probably Amal also. The taper on the metering screw is almost always damaged, which is only important if you intend to use the oiler sometime.

I know of D oil tanks where the filler neck has cracked along its mating line to the tank. You can zip tie a rag on it and figure out if the leak is coming from the tank joint or the cap.

David
 

Bill Thomas

Well Known and Active Website User
VOC Member
I wonder if Gary is useing a very thin oil, Which might make it worse, I know some people think that is the way to go, But not me.
With the breathers, You get better air flow if you fit the "D" cap over an adjuster rather than the valve.
Cheers Bill.
 

BigEd

Well Known and Active Website User
VOC Member
VOC Forum Moderator
I wonder if Gary is useing a very thin oil, Which might make it worse, I know some people think that is the way to go, But not me.
With the breathers, You get better air flow if you fit the "D" cap over an adjuster rather than the valve.
Cheers Bill.
Didn't the "D" heads have clearance up through the front exhast valve area to allow breathing up there? I think I did a bit of fettling on my "B" front head to try out a "D" cap. I've got the heads off at the moment so I'll have a look when I check the valves etc.
 

Bill Thomas

Well Known and Active Website User
VOC Member
Didn't the "D" heads have clearance up through the front exhast valve area to allow breathing up there? I think I did a bit of fettling on my "B" front head to try out a "D" cap. I've got the heads off at the moment so I'll have a look when I check the valves etc.
Yes, But I don't think as good as above the adjuster. Cheers Bill.
 

greg brillus

Well Known and Active Website User
VOC Member
Grind a small flat on the side of the upper guides and align it with the circular cut away above the rocker. That gives plenty of air space. Quickest way to destroy the looks of your engine is cover it in unnecessary breathers. Motorcycle manufacturers back then were very slow to realize the importance of the placement and size of engine breathers.
 

Bill Thomas

Well Known and Active Website User
VOC Member
I was too young !!, To know Jim Smith, So I got Brother Ron to alloy weld a curved bit of alloy Bicycle handle bar to the A.T.D. cover, Didn't want to Begger up the T/case, On one of my bikes', Agree with Greg, It did look rubbish, But Needs must.
Now the bike and me are "Out to grass ", Last year I put " Our John's" Breather Cap with a valve, On the front inlet adjuster position, Looks very neat, I think, No good to Gary, John is in U.K. Cheers Bill.
 

Gary Gittleson

Well Known and Active Website User
VOC Member
I'm going to try to answer the questions raised.
1) I am using 20w50 Valvoline oil
2) I thought of piping the chain oiler to a T fitting at the existing breather but that might pump more oil into the one-way valve that it would like. I don't like lots of breathers around either but I the caps over the valves are pretty hidden under the tank and the hoses are pretty well hidden too.
3) I checked the tank for leaks with petrol. No problem there. I did try a bit of that leak-finding dye. After a 100 mile ride, it shows up all over the rear of the tank, down onto the RFM etc.

So what of that article I mentioned? I don't quite see why one would need to plug the adjuster hole down below, instead of just screwing the thing all the way down.
I can actually see the second hole in the block.

I like the look of David's "carb slide" device.
 
Last edited:

davidd

Well Known and Active Website User
VOC Member
Gary,

When I noticed yesterday that no one had answered your question I did not think it would generate this kind of interest!

It seems to me the the oil is fine.

In general, the D breathers were a compromise due to cost. They seem to work fine if the engine is tight. I like the timed breather or a reed valve on my own bikes. The D breathers had modified top valve guides so they would pass air and oil more easily. That is a bit of work to do. Most owners want the on the rockers because that is the best way to get rid of the oil and air. Oil laying around the valves can often find its way down the guides.

I would not have thought that the D oil tank could become pressurized enough to leak through the vent hole of the cap unless something odd was happening. I know the scavenge side of the pump works twice as hard, but it only pumps what is there in the chamber. I would have thought that it would not be willing to pass air unless your crank cases were unduly pressurized. If your oil tank is unduly pressurized, I would hate to pass that back to the engine via the mod.

Based on the assumption that most things are OK in the engine, I assumed the oil weeping was from the splashing in the tank filler.

A view of the chain oiler is shown on page 19 of the Rider's Handbook. If you screw the taper into the tiny hole you can see, air and a very small amount of oil can still enter the chain oiler tube from the large hole on the right side of the block That creates a drain for what I assume is any excess oil from that tiny chain oiler hole that the metering screw works on. The only 100% way to block off the chain oil tube is to plug the end coming out of the tank.

It might be worth trying an aluminum disc under the screw to determine whether your problem is just splashing or something more serious like splashing plus pressurization from the engine. You might also run a little less oil in the tank as a test to see if increasing the air volume gives you any benefit, like allowing the splashing to subside a bit.

David
 

Top