Thinking about fixing pinholes in gastank.

[Blarfnugle]

I recently derusted my CB360's gas tank and noticed that there appear to be pinholes in the tank. I've repaired rust spots on other bikes but not a gas tank, here's what I plan to do.

1. Strip all the paint and rust off of the outside of the tank.
2. Pour some 2stroke oil and gasoline into the tank, no more than 2 cups. I do this because I have them on hand but otherwise I'd use some dye, plus the oil helps coat the inside, preventing rusting.
3. Mark where the leaks are with sharpie.
4. Drain the gasoline and wait at least 1 day for the gasoline to drain out.
5. Use my solder gun to heat up the area around the tank that has holes, melt the solder and glue on with pieces of washer.
6. Test to see if there are any leaks still.

Is this a good way to patch a tank? I've done this for metal roofing and cars but never for something like a gas tank and I'd rather not have a fire the first time I try to start the bike.

 

[The Lloyd]

Heating a tank with fuel vapours inside is not advisable, you need flush and clean the tank.

for a quick long lasting fix there is JB Weld tank repair kit that does holes up to 1/4 inch and cracks 4 inches long.

pin holes can also be fixed by lining the tank, but this can go badly if you do not prep the tank properl.

you can detect leaks without striping the paint of the whole tank. Or dripping gas everywhere , If you have acess to an air compressor, after the tank is drained and off the bike leave the cap on, open the petcock or remove, blow air into the tank thru the petcock hole or the petcock itself, you are slightly pressuring the tank, not blowing it up so not a lot of air is needed, then spray the outside of the tank down with soapy water and look for bubbles.

 

[oldjeep]

Make sure you flush tank before using compressed air, static from the air can cause a spark.

 

[oldjeep]

For my tank, I sandblasted it to find all the holes. Then used solder to fill them, then used casswells tank liner.

 

[Blarfnugle]

Heating a tank with fuel vapours inside is not advisable, you need flush and clean the tank.

for a quick long lasting fix there is JB Weld tank repair kit that does holes up to 1/4 inch and cracks 4 inches long.

pin holes can also be fixed by lining the tank, but this can go badly if you do not prep the tank properl.

you can detect leaks without striping the paint of the whole tank. Or dripping gas everywhere , If you have acess to an air compressor, after the tank is drained and off the bike leave the cap on, open the petcock or remove, blow air into the tank thru the petcock hole or the petcock itself, you are slightly pressuring the tank, not blowing it up so not a lot of air is needed, then spray the outside of the tank down with soapy water and look for bubbles.

Do you have a method that doesn't use an air compressor, unfortunately I do not have access to one.

 

[CarnivorousChicken]

If you're fixing pinholes now, you'll likely be fixing more down the road -- which would suck if you paint the tank.

I would line it, using something good like POR15 or RedKote (others use Caswell but I haven't yet, but it gets good reviews). Kreem gets almost unanimous bad reviews. That'll make sure you don't get any new pinholes after you paint. You have to follow the directions to the letter. POR15 is a 3-step process, RedKote is a 2-step process. I have lined tanks with both and they have held up for decades.

There are plenty of people who advise against tank lining, and there are plenty of occasions where it's debatable if it's necessary. But a tank developing pinholes -- and sure to keep developing them -- is one where I'd recommend it.

 

[RobMan]

On my CB450 tank it started with one pinhole which I soldered, pressure tested and another leak which I soldered, pressure tested and several more leaks. I ended up using Caswell tank liner and it worked very well sealing the leaks and trapping rust particles along the bottom seams. If I ever do another I will thin it according to the directions and and double the amount time I spent rotating the tank as I ended up with some areas of the center hump not getting coated properly. Has not hurt anything and doesn't appear to to be peeling.

 

[Blarfnugle]

If you're fixing pinholes now, you'll likely be fixing more down the road -- which would suck if you paint the tank.

I would line it, using something good like POR15 or RedKote (others use Caswell but I haven't yet, but it gets good reviews). Kreem gets almost unanimous bad reviews. That'll make sure you don't get any new pinholes after you paint. You have to follow the directions to the letter. POR15 is a 3-step process, RedKote is a 2-step process. I have lined tanks with both and they have held up for decades.

There are plenty of people who advise against tank lining, and there are plenty of occasions where it's debatable if it's necessary. But a tank developing pinholes -- and sure to keep developing them -- is one where I'd recommend it.

Wow, great point. I was scared away from lining because of what I saw on the internet but maybe I'll give it a try.

 

[GMX]

I would not put any oil into the tank in order to detect leaks, it will be hard to remove the residue when applying a tank liner and could cause it to fail.
To find pinholes, use HEET gas line antifreeze, basically methyl alcohol...it is much lighter than oil, will flow easily through pinholes or seam cracks and evaporates leaving no residue.
Place the empty tank over some brown shipping paper. The alcohol drips will indicate where the pinholes are so you can pay specific attention to them when applying POR-15 later.

 

[CarnivorousChicken]

Honestly if you do it right you won't need to know where the pinholes are (and/or will be). POR15 done correctly will line everything well. Just follow the steps -- including introducing forced air -- to the letter.

 

[crazypj]

Quick way to 'flush' gas tank, next time you take car/truck out, after it's hot, put exhaust pipe into gas tank filler hole.
it will pre-heat tank removing fuel vapor and the CO/CO2 will be non flammable.
Soldering isn't the easiest way to fix tank but is the best way if replacement isn't an option..