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Gas Tank Restoration?

4K views 13 replies 7 participants last post by  rambo 
#1 ·
I have a '72 Daytona, T100R, I am working on. I went to get the gas tank ready to reinstall this afternoon and ran into a whole bunch of issues. I had bought new mounting studs for the front of the tank and when I tried to remove the old ones I found they were both stripped where they go into the bottom of the tank. Yes, the mounting holes are stripped out!. It also looks like the front of the tank by one of the studs may have a leak. I need to get this repaired or replaced. Does anyone have a recommendation on where to get this old tank repaired?
 
#3 ·
Can you post pictures of the mounts as they are now? It would be much easier to discuss a repair once we know what has already been done, it's very common for the mounts on these tanks to require repair and possible someone has been there before and made a mess already.

Rod
 
#7 ·
Hi,

It can be fixed .
:thumb

Can you post pictures of the mounts as they are now? It would be much easier to discuss a repair once we know what has already been done,
:agree

Can the studs be brazed or welded in solving both issues of stripped threads and the leak?
this is the most common fix. It will usually fail and more and more braze is added until the tank is a mess.
With respect, I suggest waiting for Fred The OP to post pictures of the offending area on his bike's tank. Ime, late 500 tank front mountings aren't like the 650's and triples', the stud thread is further away from the bottom of the tank than the latter, and thicker, so brazing/welding the stud to the mounting might not be the only solution.

I had bought new mounting studs
Yes, the mounting holes are stripped out!
As I've posted before, your bike survived the time when Brit bikes were just cheap transport and spares were hard to come by, when a dpo just fitted handy bolts in place of lost studs. Fitting standard bolts bypassed the protecting shoulders you can see between the threaded and unthreaded parts of the studs and because, by definition, the bolts were thinner than the holes in the rubber spacers, the dpo screwed the bolts up 'real tight' ... :Not again

Btw, check the length of the 3/8" OD part of the studs against the thicknesses of the rubbers, frame bracket and cup washer; when a securing nut reaches the step between the threaded and unthreaded parts of the stud, it should've compressed the rubbers enough to hold the tank securely :thumb but not so the rubbers are bulging. :eek: Also check the thread is long enough to take a self-locking nut with a couple of stud threads poking through the nut. When I was building my T100, all the off-the-shelf studs I was offered were too short in both respects, I ended up having some made correctly by a machinist from stainless. :(

I suspect the leaking on was caused by putting the stud in upside down and puncturing the tank.
Correct late 500 studs have the same threaded length on both ends. ;)

Hth.

Regards,
 
#10 ·
Here are the pictures. Both studs were stripped on the ends when I took the bike apart. Only one stud had a nut on it and it was a metric nut that had been forced on. As you can see the other stud was broken off. The tank has been repaired before, you can see the additional weld along one side of the tab where the paint is scraped away. When I went to install the new studs I found the paint had bubbled up where some gas had seeped out. There is still some evidence of thread in one side but the other side is completely stripped as you can see by the lack of threads on the end of the stud. This was a real pain to get out!

Oh Yeah, there also appears to be some kind of reddish pink stuff in the tank. Looks like someone put some kind of sealer in it previously.

I am really looking for some recommendations on who does a good job repairing these tanks. I've googled it and found several places that say they repair tanks and use various processes from cutting the bottom out of the tank to using a caustic solution.

Help me please!
 

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#12 ·
The mount on the filler side of the tank is as it should be, welded only on two sides. It also appears this side is not leaking (check this). Carefully drill and helicoil back to stock. The other side has been f**cked with. The obvious reason for this is as has been said, someone wound a bolt in without a shoulder and likely punctured the tank. It looks like they have then tried welding around the threaded plate and when that failed tried a tank sealer that has also failed. If you do as has been suggested and braze the stud in you will still have a leak from under that threaded plate.

Your first job is to remove that sealer, it sounds like you have a product called Redcote, this apparently dissolves with acetone or MEK. It is not a fun job and you must remove all remnants of the sealer.

You can then cut out the threaded plate, repair the leak and make a new plate to replace it. Weld it as per factory. If you choose to do so you can then re seal the tank.

Marc, I can't really tell you, only that they do. Look at it as being the same as powder coat, you wouldn't simply key someone else's bad job and then wait for your new coating to fail.

Rod
 
#13 ·
Hi Rod,

Marc, I can't really tell you, only that they do.
Based on my experience and what you've posted on BritBike, I'd say it's probably all the different people having a go with both welding and brazing :( - amateur welders melt and blow holes in thin steel but as soon as there's any braze in the area, that melts and contaminates any subsequent welding even by a pro.? :Darn

Regards,
 
#14 ·
I weld tanks when they are holed.Dangerous job as the petrol fumes can ignite so they need thorough washing with soapy water.A good welder would do it easy.Possibly a good idea to make a small plate and attach a threaded tube ready for the stud before trying to attach it to the tank.
 
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