BSA Bantam - Fuel Tank Corrosion

MacJ

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I have been given a 1971 BSA Bantam which has been stored since 1985, but is complete and was in running order last time it was used. Unfortunately it was not prepared for storage and was left with a half full fuel tank. The fuel I drained out looked like creosote and had quite a bit of rust sedement in it and the inside of the tank has clearly corroded although it still appears structuarly sound.

Now I know there are some brilliant restorers and engineers out there so I'm hoping that one of you can tell me how to restore the tank to a useable state?

This is the first time I've tackled a project like this and hope to get the bike back on the road for a few summer runs.
 
MacJ said:
I have been given a 1971 BSA Bantam which has been stored since 1985, but is complete and was in running order last time it was used. Unfortunately it was not prepared for storage and was left with a half full fuel tank. The fuel I drained out looked like creosote and had quite a bit of rust sedement in it and the inside of the tank has clearly corroded although it still appears structuarly sound.

Now I know there are some brilliant restorers and engineers out there so I'm hoping that one of you can tell me how to restore the tank to a useable state?

This is the first time I've tackled a project like this and hope to get the bike back on the road for a few summer runs.
Click to expand...

Its worth assessing just how much the rust has progressed, since the bantam will have running 25/1 petrol oil mix, so this will have done some protecting.

First close the fuel tap. I would suggest you remove the tank and give it a swill with about 500 mls of white spirit and a pile of nuts and bolts and small screws. put some polythene sheet on the filler neck and screw on the lid. Then rotate and turn the tank for about 5 mins, leave it to soak for 10 mins then repeat. Pour the solution out into jug or bottle through a funnel with a rag as a filter. This allows you to catch all the steelwork and see whats been removed. The purpose is , the screws l and nuts remove all loose rust and gum caused by the poor storage.

White spirit is used rather than water, as if rust is removed exposing fresh steel and water is present then the tank will flash rust when drying.

Once its clean and dry get a bright torch and have a gander. Tanks dont just corrode at the base, my BSA had pinhole corrosion on the top rear of the tank.

If the tank didnt leak and no pinholes were seen during the washing / agitation you maybe lucky. If you have no pinholes I would avoid tank relining as A its hard to do and B it doesnt last that long. I have done two so far as both tanks had leaks , the POR15 worked , but one tank started to delaminate after eight years.

Key thing is avoid getting water in the tank, if you have to rinse then follow up with a swill of methylated spirits as this mops up the water held in the seams which is a bugger to dry out!
 
Thanks for that Steve. I'm really suprised at the level of rusting. Where does the H2O come from, the cap was on and it was half full of fuel?
I'll drop my nuts in the tank and give it a good shake, sounds interesting!
 
It comes from the air in the tank and as the tank is vented this continues as long as the tank isn't either full or completely empty. I had similar with my Honda 750 in the 80's when the welds at the bottom started to leak and used a 2 pack epoxy sealant to fix it but this needs to be done with care and I'd use either normal bolts or an old petrol tap to plug the threads on the tank as the epoxy will seal the petrol tap too. Ethenol is even more hydrophobic than petrol so this needs to be taken into consideration when storing bikes over the winter. I completely empty my tank, the other alternative is to fill it to the brim, preferably with petrol without any ethanol in it so one of the super unleaded E99s

Have a look on YouTube there's loads of how tos on there

Here's one example from our merican friends that uses toilet bowl cleaner

https://youtu.be/075mI7sKy6E
 
There are autojumbles this weekend at Kempton park, Ardingley, near Gatwick and Shelton Mallett among others.

Given the number on Bantams made there are so many parts available that it’s definitely easier and probably not that much more expensive to get a tank already sorted.
 
BillWright said:
Given the number on Bantams made there are so many parts available that it’s definitely easier and probably not that much more expensive to get a tank already sorted.
Click to expand...

+1, if the tank is in poor shape, there are usually a few Bantam tanks at jumbles. Certainly at Kempton (which is quite big), I'd expect 4-5.
 
Acetone, nuts and bolts wrap up warm and stick it in a cement mixer for 30 minutes , drain the crap out and rinse with clean acetone.

Refill to the brim with Screwfix or similar brick cleaner and leave overnight, drain and rinse with water and sodium bicarbonate or similar to neutralise the acid and you have an internally clean rust free tank.

To protect it swill around two stroke mix.

Loads of how to videos on You Tube, did an old Yamaha tank last year and it works
 
BillWright said:
There are autojumbles this weekend at Kempton park, Ardingley, near Gatwick and Shelton Mallett among others.

Given the number on Bantams made there are so many parts available that it’s definitely easier and probably not that much more expensive to get a tank already sorted.
Click to expand...

The bike actually came with a spare tank but that also seems to have rust inside and externally is not so good.

I ran into a bloke last night who collects WW2 British bikes (he also rides a GS so may be on here?) and he has a wasshing machine adapted to mechanically rotate the tank with loads of nuts, bolts and self tappers inside. He says that gets it cleaner but he uses vinegar rinse.

He also applies a sealer but we didn't have time to talk about that, any ideas out there?
 
I was in Peter Hammonds, Cirencester, this afternoon. They’re closing down and had a few Bantam D5 parts, including a petrol tank if you’re interested. They had, maybe still live, an eBay shop and may be willing to post. Might be worth a call, PM me if you would like contact details.
 

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Thanks for that but I'm starting to see light at the end of the tunnel. I threw a load of nuts and bolts plus a few screws with some white spirit in and gave it a rare old shaking. My missus came out to to see what the noise was so I told her i was just giving my enormous maracas a shake.
After a couple of hours and repeated draining and filling all of the rough stuff had gone and no signs of leaks.
I'm now going to give it an acid etching and seal it. Hopefully that should cure it. I've rebuilt the carb, put a new battery on, repaired the wiring loom and will now try to drain the old oil out of the gearbox and refill it.
Can't wait to kick it over.
 
After you acid etch and neutralise it swill it out with water, then straight away rinse out with acetone or IMS. Then put it in a conservatory or airing cupboard for a couple of days to dry.

The tank sealers are iso cyanate based and use moisture to kick them off. If you have any moisture left in the tank eg in a welded folded seam the sealer will bubble as the iso cyanate reacts with the water and produces carbon dioxide. You are then in a world of pain removing the delaminated liner.

I know it seems like Im advocating time but the tank needs to be bone clean and bone dry before you apply the liner. I know because I have lined two tanks that I had to strip as the previous liners had failed.
 
theoneandonly said:
that's sad , i used to be their paperboy , many years ago.
Click to expand...

I’ve lived in Cirencester for 33 years and used them regularly, it’s been great having a local bike shop you can trust. The staff have mostly all gone to other jobs and the site will be redeveloped as housing. It was a proper auto jumble in there on Saturday.
 
steve hughes said:
After you acid etch and neutralise it swill it out with water, then straight away rinse out with acetone or IMS. Then put it in a conservatory or airing cupboard for a couple of days to dry.

The tank sealers are iso cyanate based and use moisture to kick them off. If you have any moisture left in the tank eg in a welded folded seam the sealer will bubble as the iso cyanate reacts with the water and produces carbon dioxide. You are then in a world of pain removing the delaminated liner.

I know it seems like Im advocating time but the tank needs to be bone clean and bone dry before you apply the liner. I know because I have lined two tanks that I had to strip as the previous liners had failed.
Click to expand...
Been there, done that with 2 BSA tanks!
I was surprised how much rust was at the bottom of my Bantam tank after a winter of sitting idle. I thought incorrectly that the bit of 2 stroke oil would offer protection but water is heavier than oil!
All the tanks you may find at an autojumble will be old and either damaged, rusty, need paint etc. The new ones from India have mixed reports, cost about 250 and will need some fettling and painting.
 
Nippy Normans supply Touratech, Wunderlich, Desert Fox and many other makes of accessories.
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