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Petrol Tank Fit

ogrilp400

Well Known and Active Forum Website User
VOC Member
Dear All,
I broached this subject a few months back but I am still wrestling with it. I am having trouble fitting a petrol tank. I purchased this tank about 3 decades ago so well before the internet and ill fitting repos. The tank has all the hall marks of being an original early B series tank. Small bicycle type pump hooks, small carby cut away, no ears at the back lower and the front mounting tabs welded to the inside of the tunnel, the two angles on the front mounting tabs. The paint is also indicating as very old. I have tried fitting it up to my HRD but with the tank fitting in all the right places, eg. rear mounting screws in the center of the slots, oil tank filler in the middle of the tank aperture, the front mounting tabs are way out! I then fitted up the tank to a spare UFM and the problem is still there. The tabs also are quite a tight fit when fitting the tank over the front of the oil tank when putting it on.
Now I am am very loath to cut the front tabs and reposition them. I just do not like messing with original parts. But it is all pointing towards this is where the problem is. Note also the position of the actual tank nose in relation to the center line of the head stock. It seems too far forward when I compare it to other Vincents I have here. But the tank cannot wholly be moved back because of the oil filler.
Any ideas?
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BigEd

Well Known and Active Forum Website User
VOC Member
VOC Forum Website Moderator
Just tried fitting the tank up to a third UFM. Same thing, its just not happening.
When you purchased it 30 years ago did you see the tank correctly fitted on a bike?
If it doesn't fit on three different UFM's then you are either very unlucky with UFM's or maybe the tank was damaged and repaired incorrectly or just made wrong in the first place.
Why was it available for sale? Could it have been because it wouldn't fit on a bike?

On an item that was made over 60 years ago who is to know what has happened to the tank over the years.

Can you borrow a known good petrol tank to try on one of your UFM's
 

davidd

Well Known and Active Forum Website User
VOC Member
I think the problem is that the front tank mounts are not original. They are not the same shape as the originals and they are not welded on to the tank in the right spot. Other than that, they are perfect!

The original mounts are not as squared off and they have more shape to them as they reach the tank. The originals are welded on the same seam that the outer tank and the tunnel are welded at a bit too much of a downward angle. The mounts above bypass the original welding position and are welded directly to the tunnel. At first glance I thought the mounts were Series D oil tank mounts, but they were probably just fabricated.

A good sheet metal man can make some new mounts and put it right.

From the newish and non-stock FT4 bolts one might think there was some sort of bash-up, maybe. Here are some shots of an original unrestored Series B. The silver line on the mount is a paint drip that landed on it and made its way around.
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David
 

BigEd

Well Known and Active Forum Website User
VOC Member
VOC Forum Website Moderator
I think the problem is that the front tank mounts are not original. They are not the same shape as the originals and they are not welded on to the tank in the right spot. Other than that, they are perfect!
David
Comparing the first photos with the ones that David has posted the lugs look like the result of an inaccurate repair. Shame to spoil the paint job if it is OK but it looks like you need to do a bit of cutting and welding.
 

ogrilp400

Well Known and Active Forum Website User
VOC Member
G'day blokes. Thanks for replying. I'll start with Eddys reply. I bought the tank at a swap meet and no the bloke didn't have it on a bike. It was just on a table or tarpaulin if I remember right. The tank had that very old look even back then. I have a track record of being very unlucky so perhaps thats it. :) The bike that I'm trying to fit it to has had a good tank on it but I took it off to temporarily use on another bike that I needed to put some miles up on. This problem tank doesn't seem to fit on any UFMs which points to the tank being the problem. Its just that having spent most of my life fixing others peoples hack jobs, I am loath to take to this with a saw, given that it shows no signs of butchery.
Now Davids reply. I am sure that the mounting tabs are original both in shape and location. I have this tank (below) here with the same tabs. I have another tank being painted and another on its way here the same. I have worked on another bike that had the same tabs in the same position. It would seem that these tabs are used on early tanks with the bicycle type pump hooks, small carby cut aways and no tabs on the back.
The non-stock FT4 bolts in the UFM are just some precision machined aircraft bolts that I stuck in the vacant holes to make sure that the head stock was all in the right place. The original bolts were bodgey and I took them out years ago.
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davidd

Well Known and Active Forum Website User
VOC Member
Well, you make a very compelling argument that they are original by having two tanks with the same front mounts. Also, they seem well thought out. I do not have much experience with the very early tanks without the steady tabs and the pump mounts. I have owned the small carb cut-out tanks, but they had the other two items. So, assuming it is original to the earliest of the post-war tanks and it is correct, also assuming nothing looks bent, it would seem that the fit is off for some other reason.

I wonder if the tightness going over the oil tank is not a result of the two halves of the tank "clam shelling" inward a bit. You may not want to put up with the fix of stretching outward slightly and just put up with the bother of the tight installation.

This still would not account for the tank being too high and too far forward. Is it possible that these early tanks were more "custom" fitted than the later tanks. In other words, if you don't put in the rear bolts and you don't care about the oil hole, can you get the front bolt hole centered? It does not look like this will work. It looks like the tank may not go low enough. If so, I think I would cut the mounts off and re-weld them. I know this does not sound good, but I once painted a D tank before I realized the rear mounting tab was missing. I welded it on with no damage to the paint outside the little pocket. These early mounts of yours are not welded to the seam except for two spots, so most of the welding is on the tunnel which will never show. This can all be done with damp rags and stitch welding. If this is a correct original item it is certainly worth preserving, even if it needs some adjustment.

David
 

davidd

Well Known and Active Forum Website User
VOC Member
hard to tell much, but this picture from late "46 has similar tabs:

http://www.thevincent.com/Factory7HRDTankUFMBolts.jpg

I'm not sure you have to cut them off. It looks like taking a wedge out and rotating them down would do it, and the welding heat later could be isolated to the tabs.

Ron

Ron,

That is precisely the same photo that convinced me I did not know enough about these early tanks.

David
 
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