A10 plunger fuel tank

[terryk]

Hi all, I have noticed there are two sorts of plunger A10 fuel tanks. One has slots at the back where tank attaches to bolts on the frame and the other tank has rings that the bolt goes through. I'm under the impression at this point that the slot ones are for 1950- 52 and the rings are 53 on is this correct does anyone know for sure. My bike is 51.
thanks

[Beezageezauk]

Hi Terry, 

You are quite correct to realise that there are two basic types of A7/A10 fuel tanks.  The ones with the slots fit the rigid and plunger frame models and the ones with the single bolt top mounting are for the swinging arm models.  The one you need for a 1951 model is the type with the slots.

Beezageezauk.

[G/F DAVE]

Hi, Terry I have a 1952 Goldflash the tank that is fitted has the rings at rear  these are for rubber mounts it has slots at the front, I also have a 1953 frame this has same rear mount as 1952  frame but front mounting has sleeved rubber inserts, I think either tank will fit both types of plunger frame . I,m sure my tank is the later type to suit frames the with rubber mountings front & back ie; 1953 onwards, hope this is of help to you. ?? all the best Dave

[a10 gf]

Never tought about it before, there seems to be two different a10 plunger tanks, one for the cowlheadlamp model and one for the no-cowl. See page 179 and 187 in bacon's bsa twin restoration. On the no-cowl there are cut-outs for the rear bolts, and bolts are slightly visible both rear and front, with visible mounting flanges in front.

Hope this helps.
E

[terryk]

Hi again, Hey all you a10 plunger 1950 - 53 owners who has rings at the back to attach tank and who has slots. What year is you bike.
I have two different tanks both need repairing. One has rings and the other has slots at back. I want to know which tanks to use so I can spent the time fixing it, my bike is 51.
I think at this stage 50-52 has slots and 53 on has rings when headlight cowl was introduced. I know there is a later tank with a hole thru tank top but I want to know about earlier ones.
thanks in advance. Terry

[G/F DAVE]

Hi, Terry the one for your 1952 frame is the one with slots front & rear, I have the later rubber mounted type fitted to my 1952 flash so  you could use either of your tanks. I,d go for the one in the best condition. All the best Dave...

[a10 gf]

Some pictures

rear non-slot tank
http://www.a7a10.net/BSA/bsapics/BSA11.08.04.jpg

rear slot tank
http://www.a7a10.net/BSA/bsapics/i-6_B_L.jpg

+ on page 13 in "BSA Twin Restoration", there is a picture of a 1951 w smaller chrome tank with apparently no slot for the seat, looks like an earlier A7 tank size.

Then, in Bacon's "twins and triples" I find the pic of a non-slot tank on a 50' plunger, so now I am confused! Anybody know the exact story and dates?

[Brian]

Thought I would see if I can confuse the issue even further ! My 53' plunger has rubber mounts back and front. Where it gets a bit harder is with the smaller A7 tank, the early ridgid and plunger ones have holes at rear to mount and the mounts are closer together. My 51' A7 has slots and the mounts are wider apart so you have to use spacers the same as the A10. The good news is that they are all interchangeable, I tried them, the only thing is you need the two spacers at the rear if using the wider mount tank. Does anyone know for certain if any A10's had the smaller A7 style tank fitted at the factory. I have seen plenty of them on bikes but have yet to see a original photo of one on a bike.

[Simon59]

Hi All. Just to add to the mix, my 1954 plunger A10 fuel tank has rings at the rear that a bolt goes through to fix it to the frame. The rubber inserts in the rings were rotten but I will replace them with something suitable if I can't get the OEM items.

On the subject of tanks, can anyone recommend a company (or DIY process) to de-rust and seal the inside of my tank? The bike hasn't been used for 46 years, so nothing has been done to it. I believe the rust can be removed with drain cleaner acids, but these are hard to buy now and I would probably prefer someone else to do it if the cost is reasonable. Is Petseal the best sealant?

Anyone's good experiences or advice appreciated!     

[Peter Gee]

Do NOT use Petseal, ethanol turns it to gum in a few years IMO. I use POR from USA and there are others.

[BSA_54A10]

Hi All. Just to add to the mix, my 1954 plunger A10 fuel tank has rings at the rear that a bolt goes through to fix it to the frame. The rubber inserts in the rings were rotten but I will replace them with something suitable if I can't get the OEM items.

On the subject of tanks, can anyone recommend a company (or DIY process) to de-rust and seal the inside of my tank? The bike hasn't been used for 46 years, so nothing has been done to it. I believe the rust can be removed with drain cleaner acids, but these are hard to buy now and I would probably prefer someone else to do it if the cost is reasonable. Is Petseal the best sealant?

Anyone's good experiences or advice appreciated! 

Best thing to do is clean the tank then unless there is a hole, don't touch it just remember to keep it full most of the time and occasionally drain it totally to remove condensed water.
Hydrochloric acid will remove rust from the inside of a tank and you can get it from any swimming pool shop in 5 gallon tubs.

[BSA_54A10]

Some pictures

rear non-slot tank
http://www.a7a10.net/BSA/bsapics/BSA11.08.04.jpg

rear slot tank
http://www.a7a10.net/BSA/bsapics/i-6_B_L.jpg

+ on page 13 in "BSA Twin Restoration", there is a picture of a 1951 w smaller chrome tank with apparently no slot for the seat, looks like an earlier A7 tank size.

Then, in Bacon's "twins and triples" I find the pic of a non-slot tank on a 50' plunger, so now I am confused! Anybody know the exact story and dates?

Most likely one of the 1000 errors in every Bacon book.
You should treat them as coffee table books not reference material.
The only worthwhile parts of them are the apendicies at the back.

All he did was add a bit of text to link BSA factory press releases together.
Most of the photos are from the same source so they are what the advertising department said the factory was going to make FOR THE UK MARKET next season and not necessarily what the factory actually made.
OTOH the tables in the back of the Restoration Guide which were compiled from the parts books would be a lot more use to you.
Again it is UK SPECIFIC but it does clearly show when a new tank was introduced and how long it got used.

You also have to remember that BSA's production time preceeded computer controlled inventory and BSA regularly ran out of parts
So the fitting of substitute parts was not uncommon, be they parts from a different model that would or could be made to fit or parts bought in from an external supplier.
BSA made their own tanks, but if the presses were set up to make Bantam tanks when they ran out of A 10 tanks, the last 10 tanks needed to fill the order currently being made would be sourced externally , if they could not be pinched from the spares warehouse.
Considering just how easy it is to damage a tank and A 10's are now old enough to draw a pension there is no reason to believe that any bike is still wearing the same tank it left the factory with.

[Simon59]

Thanks Trevor. So you would de-rust the tank but not seal it? Sounds sensible if keeping the tank mostly full and draining it for the winter reduces the effects of the dreaded ethanol.

I've read a very interesting article online (from RealClassic.co.uk) that suggests using sodium hydroxide (caustic soda) to remove any gunge, then hydrochloric acid (spirits of salt) to remove the rust followed by a rinse of phosphoric acid to protect the newly cleaned surface.

Whilst all these chemicals are relatively cheap, a recent spate of acid attacks (really!) in the UK has made them difficult to buy.

Sounds like a bit of a faff but I'm desperate to hang on to my original tank rather than buy an Indian after-market replacement, but after 46 years in the back of a damp garage, my tank is pretty badly corroded inside.

[Greybeard]

My tank came back from the platers rusty inside. I lined it with POR15. We don't have as much ethanol here in the UK.

[Rex]

Yep, POR15 for me too. Did a Scott tank with leaky seams and it's really effective. Make sure you put a blanking plug or old duff taps in the outlets though!