Plastic Gas Tank Repair

massacre

massacre

#1
#1
Hello,

I have a leaking plastic gas tank, tried regular JB weld on it and it lasted for a few days then failed.
I was going to use the plastic JB weld but it didn’t say whether or not it would withstand gasoline.

Looking for something that definitely works, could I ‘glass it? The crack/hole is not large but it’s on the bottom so has to be a good repair. Something easy would be great but if not difficult is ok too lol.

Should I sand out all the remaining JB weld from the previous repair? It’s an MTD tank so I don’t want to have to find another one.

Thanks for any feedback
Have a nice day
 
H

Havasu Dave

Moderator
#5
#5
Epoxy, or any other adhesive is not going to work as a permanent repair. You can dig up this information on chemical adhesive bonding to various plastics. I tried for a damn year to repair a plastic tank, including Caswells tank sealer on a roughed up surface, various epoxy mixtures like JB weld, etc. And no, FRP is not going to work. I am referring to "fiberglass" which includes epoxy or vinyl depending.

The only thing that repairs plastic tanks is a plastic weld. (heat) I made a plastic welder out of a hot glue gun and strips of a late model Tecumseh tank.

The Caswell's lasted the longest of all the repairs, but since it does not adhere to plastic, (it too is an epoxy) it shrank within the tank just enough to allow fuel to seep behind it.
 
Davis

Davis

Well-Known Member
#7
#7
I’ve been using it for years and it has worked very well. It is on that cat tank and is full of gas and still holding well . Another custom bike trick with it is when you weld a hideaway gas fill on is to put a ring of this about a 1/4 inch down on the throat and I have done many and still holding strong. I even put it over a pinhole on a small Briggs tank on the bottom 5yrs ago and still holding and is hard as a rock. I didn’t figure this one out it was taught to me by a few friends that work at kindig in salt lake.
 
massacre

massacre

#8
#8
Well I typed out a huge thing and then lost connection and it got deleted

Thanks Dave for the tip on an old gas tank, embarrassingly I didn’t think of that.
Are they all the same type of plastic?
Like will late model plastic jive with early ‘70s plastic?

It’s good to know that there are other options in case I fubar it lol
 
capguncowboy

capguncowboy

Well-Known Member
#9
#9
Yes, plastic welding. If you don't have a hot glue gun you want to sacrifice, you can use a soldering iron. It takes a little longer but it works with some patience.

Does anyone know what the tanks are made of? Polyethylene? You can buy just about an polymer in nearly any color imaginable that should be compatible with hot glue guns. I cut a chunk off a black stick of polyethylene to fix the tank on my Hilltopper. Nearly 35 hours of riding trails and off road later and it's still holding up just fine.
 
capguncowboy

capguncowboy

Well-Known Member
#11
#11
massacre said:
I can buy a cheap hot glue gun just gotta find the right plastic
Click to expand...
unless we can figure out what sort of plastic it's made from, you might be better off finding a sacrifcial tank to cut pieces from.

I would bet it's polyethylene if it's an MTD tank. That's the right era for it but it'll make a mess if it's not.
 
Davis

Davis

Well-Known Member
#12
#12
Also I would like to note I do have a plastic welder and this stuff will repair a crack in a car bumper and hold better with backing.
 
massacre

massacre

#13
#13
capguncowboy said:
unless we can figure out what sort of plastic it's made from, you might be better off finding a sacrifcial tank to cut pieces from.

I would bet it's polyethylene if it's an MTD tank. That's the right era for it but it'll make a mess if it's not.
Click to expand...
A sacrificial MTD tank? Oh man say it ain’t so lol
 
H

Havasu Dave

Moderator
#14
#14
I want to say HDPE. I used an old Tecumseh tank because the texture was identical. You know the tanks I mean: The new ones, with a giant fill cap in the center that you'd never put on a mini bike.

In hind site, I would have been better off getting an inexpensive plastic welder. Look on line and there are charts that describe types of plastics and their characteristics. Then get some appropriate rods.

And now that I think of it, if you have a rare tank, it might be better to send it out to someone qualified to do a professional job of welding on it.

[MENTION=53707]Davis[/MENTION] I have never tried the epoxy you cite. My resume is pretty long on some of these adhesives including Mil-Spec fuel tank sealants, and if it isn't chemically bonding to the plastic- in other words, if you can scrape the cured stuff off with a finger nail, it's a leak waiting to happen. Rubberized car bumpers aren't difficult. I know you're in the collision business. But you can repair those with polyester resin or any epoxy mixed with a substrate to provide bulking. For $38 for that tiny bit, your stuff better fashion itself into a fuel tank, and "then" fill itself full of fuel, and turn around and kiss you. :laugh:
 
H

Havasu Dave

Moderator
#20
#20
derekbmn said:
PM sent massacre.....I can help ya out with this :thumbsup:
Click to expand...
Derek, make it public. Or send me a PM too because I once spent a year on a Cat tank. (the expensive one) The longest I got the fuel to not vapor out, (never really was a leak) was several months- long enough for me to apply the rare trim tape on the bottom and custom made tank decal one more time.
 
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