Braze Gas Tank

So a bit of a backlog, my GF picked up an 83 xs400 maxim for a few hundred bucks(which is why Im posting in other motorcycles). The engine and transmission is very strong. Bike over all was a tad rough, seat ripped up, tank dented up and jb-welded, front forks bent slightly, blinkers not working.

Ended up going to the local junk yard and finding a very nice set of forks/triple tree, seat, tank, blinker module and some other minor extras at a good price. Needless to say its coming along very well with one exception: the tank.

Did the whole CLR and BB thing to clean out the thank just in case. Glad I did since after while rinsing out the tank I some small pin holes leaking right near the bottom seam. Sanded it out and it did not look bad at all so I figured a quick braze job would work wonders to seal it up and get her on the road(shes very impatient/excited). Turns out that brazing was a bad idea as the heating of the tank caused heat stress cracks to exacerbate the problem and every time I patch up a leak somewhere else ends up with another leak from the heat radiating out. Its very frustrating to say the least.

Im going to try grinding down the braze and see if I cant give it one last try brazing the bad sections and then possibly soldering over any small spots(wish I would have started with the solder first). At this point I think the tank might not be worth the continued effort. Kinda sucks since the tank was not exactly cheap, but not enough to really care to go back to the junk yard.

Her original tank is not terrible, but someone tried to remove the emblem bars and ground through the tank when they were cutting the welds. I can probably jb weld those holes and smooth it over to make it look decent, but I would feel much better about knowing she has a solid tank than something somewhat cobbled together.

I guess if anything Im asking for suggestions on what others have done with small tank leaks.

 

Why not reline the tank? Caswells has the best kit there is for the job.

 

I like the idea of relining a tank, but my area has e-10 gas, soon to be e-15 in the future. I have not heard many great reports about the tank liners lasting terribly well with higher concentrations of ethanol gasoline. I planned on lining the tank, and for myself I would probably just do that and carry on. But it falls into a sense of safety comfort having the girl I plan to ask to marry in the relative near future riding a bike that could potentially start spilling fuel onto the engine and exhaust if the liner were to fail. This is mainly why I wanted to try and get the leaks sealed up proper in a way I know will last for some time.

In the end Im probably over thinking it all too much and over complicating things but for her I just want to be sure the bike its self is safe. I considered buying another gas tank and gifting it to her, but so far I have not found much other than dented up rusty crap on fleabay for $150 bucks or more.

 

Great stuff! It's what I use. If you've got big gaps just tape over them and remove the tape/sand after the epoxy sets.

The Caswell is epoxy. It sets by a chemical reaction, not solvent evaporation like Kreem. About as inert as you can get. You should be able to fill it with straight ethanol and have it last 1000 years.

Once the rest of the motorcycle rots away to dust there will be an epoxy fuel tank laying on the ground.......

Of course you need to make sure not to get any where you don't want it because the only way to remove it is cutting/grinding/sanding/drilling etc.

 

Not only is it epoxy...it's the same sort of epoxy that is used to line underground fuel storage tanks....the ones that hold ethanol, and ethanol blend fuels. The key is being certain that you prep the inside of the tank EXACTLY as Caswell directs.

 

Ah sweet I did some googling on that brand and it does sound a bit different from the other stuff I have been reading about. Ill have to get some ordered and coat her tank along with mine as well. Aside from general inner tank prepping such as using BBs and CLR to descale the tank any suggestions to get as much of the crap and rust out of it as possible?

 

I've lined 2 tanks with it. One of them was an XS400 Seca that was swiss cheese, had so many holes. That stuff is freaking amazing.

 

Basically you need to get all the petroleum and residue out, any severe loose rust off and have it be good and dry. The instructions say it'll adhere better if there is some surface rust.

Since Caswell is clear and I'm doing customer tanks I remove surface rust too. It's difficult to get paid for coating a tank that looks rusty afterwards.

Here is my process:

Rinse with a bit of lacquer thinner to get fuel and residue out.

Warm soap and water soak and rinse, only add hardware and shake if the tank has sever flaking rust. Rinse well.

Phosphoric acid to remove any rust. (Caswell recommends leaving the surface rust).

After the phosphoric acid another soap and water wash then lots of rinsing with cold water.

Immediately rinse with some lacquer thinner to get the water out, otherwise it will flash rust. That flash rust is only an appearance problem, it won't hurt the stick of the coating.

Then I like to let it sit in the sun for a few hours to completely dry it.

Follow the directions for the epoxy. They will warn you about using it if the temperature is excessively warm or cool. I've never had a problem with it curing too fast, but at 70 degrees it flows very slowly. Seems to work great at about 80 degrees (F).

Once the tank is coated it will take a long time for the excess to drain out. I like to have a deep box that a tank will sit inverted over the open side. Line the bottom and sides with newspaper and place a plastic coffee can under where the fill neck will be. Add some crumpled newspaper or packing material to hold the can in place. Then I let the tank spend an hour or so there.

Once the excess material has drained you need it back upright or it'll end up with little epoxy stalactites rising from the fill neck.

When it's getting more firm but before it completely sets I use a blade to remove any that will interfere with the fuel cap. That can of excess you collected can be used to judge when it's ready. I also trim out the openings for the fuel cock and level sender so those parts will slide back in. Then I oil up a tap so the epoxy won't stick and chase all the threaded holes.

Let it finish curing and put it all back together.

I don't think this applies to any XJs, but some tanks have nipples for vent pipes. I blow those things out with compressed air frequently during the process to keep them from becoming sealed up.

 

I think I can handle that. On a side note that is a really well written up instructional for the process, not sure how often this comes up as a topic on here but it could come in useful for others also. Thank you for the directions with it I will likely print it off and use it as a checklist while Im lining the tank.