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Gas tank repair methodology

Big T

Big T

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I recently bought another 78 GS 1000 and it came with a "spare" tank

The bike's been sitting on the trailer under a tarp because, well, it's winter.

I thought I'd work on what I could, so I pulled the crappy looking spare tank out of the box and start grinding on it. I used paint stripper, then a stripping wheel to knock of the 4 layers of crap paint and try to take some of the dents out of it.

There was a big blob of body putty at the left rear, when I ground that off, this is what I found

gastank001.jpg


The tank is lined with Kreme or something, so that's what must be holding any fuel in. The rest of the small bottom fold has lots of pinholes in it

gastank003.jpg


The right rear has already been "repaired" by what appears to be an arc welder.

gastank004.jpg


The right bottom also has a bunch of smaller holes

gastank005.jpg


With the smaller holes, I thought I'd bathe them in Evapo Rust to clean then, then use Gas tank repair putty or JB Weld to fill

On that pair of craters at the left rear, Should they be TIG welded? MIG welded? Some thing else?

Should I plan on stripping out the lining for these repairs?

Don't be telling me to toss the tank. It's a 78 and they're real hard to come by.

Oh yeah, I'll be grinding off that lovely weld at the right rear and seeing what I've got there.
 
Given enough time and money you can repair anything but I hate to say it but that tank is probably not worth repair. It probably has a lot of rust that you can't see like in the second last picture, all those little black marks are probably rust spots from the inside just waiting to come through. I'm sure someone here has a much better tank than that for cheap.
 
The proper repair technique involves cutting off the bottom of the tank so a proper sandblasting and inspection can take place. All the thin sheet metal should be replaced, not just fix the holes. A lot of work and expense to be sure but doable.
 
Sandy said:
Given enough time and money you can repair anything but I hate to say it but that tank is probably not worth repair. It probably has a lot of rust that you can't see like in the second last picture, all those little black marks are probably rust spots from the inside just waiting to come through. I'm sure someone here has a much better tank than that for cheap.
Click to expand...

Sandy, it's unlikely many people have a spare 78 tank. It's unique to the 78 GS 1000. Plus, this is a spare. I've already got 2 78s , each with a tank. I can spend all the time I want on this one.
 
Nessism said:
The proper repair technique involves cutting off the bottom of the tank so a proper sandblasting and inspection can take place. All the thin sheet metal should be replaced, not just fix the holes. A lot of work and expense to be sure but doable.
Click to expand...

Ed

So, basically my next step is to strip out the lining so I can see the bottom from the inside and see if they covered up rust on the inside also?
 
You could clean up the surface rust spots that you see and then run an internal tank cleaner & resin liner kit (por-15 is one that comes to mind) through there to seal up any corroded spots inside the tank. I am currently using my "spare tank" and one of the steps i envision taking is to clean up the external rust as well as running that "por-15" kit i mentioned through the internals on the tank to make sure it's all good internally.
 
My tank looked like that.
I buffed with a wire wheel and got ALL the rust off, then gave it a shakey shakey like mad with pea gravel in it. Then a vac and rinse with MEK. Used a metal epoxy to plug the holes. Then had a rad shop line it with "Red Kote".

Works like a dream.

Edit. I actually had the same problem with my 750T and followed the same procedure.
 
I've done some tank work so here goes.

!) Don't sand blast it, unless you want to ruin it. (Sandblasting will deform this thin sheet metal). Take it somewhere and have it chemically dipped to remove the rust and old bondo. You need to know where you stand.

2) The best way to fix the holes is to pean them in slightly and then weld in a new piece of sheet metal over the peen, grind down the excess and then use a GOOD QUALITY filler - not Bondo for god's sake. Don't try to fill the holes and grind them down. The metal is too thin and you have a real hard time getting it right.

3) The metal is pretty thin so you need a MIG or TIG. Have someone weld it if you can't.

4) Sand, prep, primer, sand ..... paint.
 
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Just to expand on what reddirtrider said. I attempted a similar repair. My tank was basically like yours in terms of condition. Get the Kreme boiled out at a radiator shop. That should also get the rust out. Next unless you are a very competent welder, don't weld it. between the already this sheet metal and the further reduction by rust, it will be tough for someone who isn't very good. Once it is clean don't seal the holes with JB. Have a welder do it. You can get a pretty decent tank when they show op on ebay for about $200 plus depending on condition. I do have a spare. No, it's not for sale. Sorry. Best of luck. These tanks are very fussy. 70's era Japanese steel is pretty cheap quality and doesn't really stand the test of time.
 
drhach said:
Just to expand on what reddirtrider said. I attempted a similar repair. My tank was basically like yours in terms of condition. Get the Kreme boiled out at a radiator shop. That should also get the rust out. Next unless you are a very competent welder, don't weld it. between the already this sheet metal and the further reduction by rust, it will be tough for someone who isn't very good. Once it is clean don't seal the holes with JB. Have a welder do it. You can get a pretty decent tank when they show op on ebay for about $200 plus depending on condition. I do have a spare. No, it's not for sale. Sorry. Best of luck. These tanks are very fussy. 70's era Japanese steel is pretty cheap quality and doesn't really stand the test of time.
Click to expand...

Well, I have a very competent welder available. One of those guys who can fix or make just about anything.

I think the last 78 1000 tank on Ebay went for $500+. It was posted up here, but I can't find that post.
 
Big T said:
Well, I have a very competent welder available. One of those guys who can fix or make just about anything.

I think the last 78 1000 tank on Ebay went for $500+. It was posted up here, but I can't find that post.
Click to expand...

I think it was $200, and several other people posted that they have found similar tanks for under $100.
 
Big T said:
Well, I have a very competent welder available. One of those guys who can fix or make just about anything.

I think the last 78 1000 tank on Ebay went for $500+. It was posted up here, but I can't find that post.
Click to expand...

You can get em for around $200, give or take. Search ended ebay auctions, you'll get an idea what they go for. $500 might be for an OEM new in box tank. It varies though, just like everything. If you have a really really good welder at your disposal, cut the tank open, clean it and re-weld it. It's going to cost you more than you'd spend on a decent tank though. I said that i tried this. I should also say that I was unsuccessful. the area around the petcock, where the rust holes are, is really thin and its fussy to weld because of the rust. Take pictures if you get it to work. I'd love to see it.
 
Big T said:
Dented, bad paint and ,oh yeah, all rusted along the bottom edge

Probably not as bad a mine,tho

I think I'll just get a POR 15 kit and strip the Kreme out and see what's inside before I move on with it.
Click to expand...

Caswell Epoxy is much thicker than Por-15 sealer, and would be more appropriate to bridge holes in the metal. Of course, bridging any kind of hole is not recommended for a lasting repair.
 
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