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Cylinder head oil feeds

kettlrj

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VOC Member
I am re-building an A Comet engine for a friend and have come to the point of connecting up the cylinder head oil feed. The normal system is for there to be two pipes feeding from the cam follower housing, each fitted into a metering union.
This engine has only one feed hole and the oil pipe is in one piece that is bifurcated at a banjo at the lower end. I have two of these pipes to choose from so it seems that it is not a one off special, but I have looked through many photos of A's and cannot find a shot of a similar arrangement. I will have to make a new fitting into the housing that has a metering hole in it that needs to be bigger than the hole in the normal fitting as it will be feeding two pipes, not one. Does anyone else have this type of oil feed and if so, do you have any details of the fitting into the housing.
Regards Richard
IMG_1786.JPGIMG_1787.JPG
 

vin998

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VOC Forum Moderator
You have an early series A single there which did have the single feed to two pipes. I'm not sure when they went to two totally seperate pipes, but probably sometime in 1936. As for how the early fitting works exactly I cannot help but I do remember Bob Stafford saying the pipes had to be crushed slightly to alter the feed as the exhaust requires more oil than the inlet.
This is from the 1937 HRD instruction book if it helps

1937 hrd instruction.jpg
 

Dinny

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Hi Richard,

I have an early 35 bike I’m rebuilding that has this setup. I have the fitting but no pipes. See below, it does have an oil flow adjustment that screws in from the top and I have always assumed it was a mod but not sure.

Let me know what dimensions you want and if your spare pipe setup is available to buy as mines missing.

09C90398-D86C-4820-A0B5-7A3F8243C130.jpeg
Cheers
Mark
 

kettlrj

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VOC Member
Hello Mark,
The valve design is not what I expected. It is almost as if it is designed to be adjusted on a regular basis, perhaps to change the flow rate after the engine has warmed up. The follower housing on this engine has been tapped out to 3/8" BSF and the banjo fitting on the pipe has been opened out to suit. The spare pipe is the original size. My friend for whom I am re-building the engine does have another engine which may also have this arrangement so I will ask him about the spare pipe.
Regards Richard.
 

A_HRD

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Richard,
My Series A TTComet started it's life being built in the factory Nov 1935 and surfaced towards end Feb 1936 (having first failed it's road-test!). Attached are photos of the original rocker-feed bits - and a few misc bits I found in boxes that came with it. Simon is right (of course), the move to two separate pipes was in 1936; and from my research and observation of other Series A bikes, this was likely around June/July 1936 - but it probably evolved over many weeks depending on spares availability, no fixed date. Either way, the adjustment comprised of very light peening of the jet hole in these early machines - on a trial and error basis. Once done, I guess the thinking was that it shouldn't need doing again! Later machines had tiny threaded adjustable outlets.
Dinny's adjuster arrangement certainly looks like an owner mod.
3/8 BSF re-tapping is huge - looks like it broke through and had to be welded too.

Peter B
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P1020442.jpg
 

Dinny

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VOC Member
73C9C66E-F142-473C-B97B-FD5D61BB3CFA.jpeg83C6E2E2-08C2-438A-ACD6-DE069135C7A6.jpeg
I always assumed it could be a factory mod. The factory were playing around with all sorts of things on the oiling side at that time and it’s well made. There are some mods mentioned in the build sheet that are hard to identify and I have seen two more very early bikes with an oil adjustment screw in the top. My engine is probably the first to have the flanged Cambox fitted.

That said, I don’t know. I will probably refit it when I build the top end this winter as it’s a part of the history if nothing else.

See pictures of both sides of the fitting, it has different size oil holes each side and the larger hole is peened over as above.

Cheers
Mark
 
Last edited by a moderator:

kettlrj

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VOC Member
Hi Mark,
The latest feeds opened up as I sent my message.
Your stud may have different hole sizes but will have no effect on the flow to either pipe because the stud is wasted where it sits inside the banjo and so the oil will flow around the stud and provide equal amounts of oil to each pipe. Also as the stud is screwed in there is no way of knowing where the holes end up pointing.
Regards Richard.
 

Dinny

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VOC Member
Hi Richard,

No problem, I can make one easily. I showed both different hole sizes to show how the oil flow had been adjusted, probably at the factory by putting a bigger hole in one side and then peening it as it was probably too big.

I guess the oil flow to each rocker is adjusted by flattening the pipe as Simon said.

Thanks
Mark
 

vin998

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VOC Member
VOC Forum Moderator
Peter
That oil pipe of yours with the one into two junction box looks just like a Royal Enfield Bullet rocker feed pipe. I wonder is one of those could be modified. Here is a photo I just grabbed off an eBay advert of one.

Simon

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kettlrj

Well Known and Active Website User
VOC Member
Hi
I was at the National Motorcycle Museum to look at details of Sturmey Archer gearboxes and took a look at the series 'A' in there. Below is a photo of the rocker oil feed which is a way of converting a single feed to a dual feed with the metering jets fitted. This seems to be better than squashing pipes or peening over holes in fittings.
 

Attachments

Dinny

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It’s an interesting mod but I think peening and squashing pipes is all part of the 30’s charm and it’s worked for 80 years.

Mark
 

vincenttwin

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VOC Member
My rocker box was welded up and two feed holes drilled for two pipes and little metering valves put in.
 

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