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Fiberglass Repair Question

3970 Views 31 Replies 19 Participants Last post by  LongHair
I unfortunately discovered a leak in my XR style fiberglass gas tank.
I dont have much experience w/ fiberglass, so what are my options?
Whats the easiest way to repair?
Just resin?, Resin and cloth?, Resin and mat fibers?
Completely different technique?
Whats recommended to rough up and prepare surface?

The leak is seeping from a seam on the bottom rear edge, circled in pencil.

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i've read a few discussions about the new fuel blends attacking the resins in old fg tanks.
A lot of gas stations have fiberglass pipe I am sure it is made to be compatible with the new fuels but it is all glued together you could probably use some of the glue to fix the tank there are two brands ao smith and ameron I think one company owns both now both brands have a filler you can add to make them thicker
Many years ago I owned a fiberglass Lotus sports car. Back then a friend gave me the best fiberglass advice ever:
Don't try it yourself. Go to a guy who does it for a living.
My friend was right. What took me forever with soso results was done by Teddy my then goto fiberglass guy in 15 minutes. So look for places that repair sportsbikes or the local boat marina or an airport where they build experimental small planes.
Look for a guy with excitement in his eyes when you explain your problem and you will be in good hands.
Add to the fact that where the fuel leaks out of the glass, might not be the place where it gets in. I'd be going for an internal remedy first.
You can clean and v groove the crack add resin to the crack first itll kinda activate the old glass then add mat and more resin then more mat..Make sure you roll out the mat with a fiberglass roller to get All the airbubbles out of it then sand to how you want it to be.I would think about lining that tank with a tank liner even though I hate tank liners I bet that tank is pourous in the inside..
If it were mine...
The exterior is an easy fix with a little mat and resin. Sand and clean the wound of all loose bits and dirt, all paint, degrease etc. Mix resin to proper consistency, (the mixing part takes practice to get it right, too much or too little hardener makes a BIG mess..follow the directions)
Have "mat patch" cut to size and ready on kitchen wax paper, pour resin over mat. Work resin into glass with small brush. (This seems to work best with a dabbing motion). (Gloves help. If you get it on the gloves, get a new pair or the stickiness will just piss you off). Press patch, wax paper and all, onto wound and squeegee the wrinkles out from under the wax paper. Wait for it to set up. Remove wax paper. Sand to perfection. May add more resin with small brush to fill imperfections after sanding and cleaning.

I would figure out what caused the rub mark and possibly protect it with a piece of split rubber hose or such. You might "patch" the other side to protect it as well.
There will be plenty of all the materials to practice with in even the smallest fiberglass patch kit.
Remember this is a chemical does get hot.
More hardener=faster cure time=more heat.
I would do the interior seal thing once the exterior has been stabilized (that would take me a little research as to what type to use for today's fuels)...
Good luck!
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Super easy fix, just buy a surfboard ding repair kit. I hate tank sealers but the only time I think it's prudent to use one is on a fiberglass tank. If you want to pay the shipping sent it to me and I will fix it for free.
Im going with a lot of fiberglass on my De-Raked Generator Shovel project.
Ive got this fiberglass tank I'm running along with a fiberglass rear fender.
Plus a lot of Stainless Steel.

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Super easy fix, just buy a surfboard ding repair kit. I hate tank sealers but the only time I think it's prudent to use one is on a fiberglass tank. If you want to pay the shipping sent it to me and I will fix it for free.
Thanks for the offer, its appreciated.
I already did the fiberglass resin / mat repair.
What sealer is recommended?
Im not sure if there is a specific sealer made to work w/ fiberglass?
You will get many opinions about sealers.. I hate kreem. I use northern/redcoat. They are the same just different colors and distributers. Caswell is popular as well.
.......I feel your pain......:(

Hope you have better luck then me .....


What you see here is the Kreen sealer or what's left of it....

Short time cure for a leak....It became hard as a three day old brisket....And stated to flake off...

What looks like oatmeal is the glass with the risin ate away.

Cut the tank open for sanding down and a new layer of glass....
Then a coating over that ....Still was a poor repair.....
......................Leaked Again.......................

Choices was a bladder to be installed...that takes up gas capacity. With only about 3 gallons to start off with...Didn't care much for that idea..But kinda still kicking around the idea some....

What I want to do is a bit hard for me to afford ..... Get a new tank.

This one is 22 years old.


Much Luck in your Quest.

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Redcote states not for use on fiberglass or plastic.
Looks like ill go w/ the Caswell.
Ive heard you can use POR15 but not 100% sure on it on fiberglass you can check it out..
Since it's already fiberglass, and assuming you could get the inside clean a liner of sorts could you mix up a batch of polyester or epoxy resin and dump it in & slosh it around?

Doing a little research, seems many boat guys are now replacing their 'glass tanks with aluminum ones to get away from the ethanol destruction.
If you run only non-ethanol gas, it would probably work well...

But......How in the world can you do that on a street bike..???

You will be out in the middle of "No-Where" and will be needing fuel....

My XR had 12.5:1 compression .... No choice but to run Turbo Blue race fuel..In the shop was a 55ga drum with a map on it..
On the map was a 60 out from home circle draw-ed....

That would let me get home from a ride with very little fuel left in the tank...
Tried to run Ava. 100 Low Lead in it a few times....
It didn't like that fuel at all...Had to remove the point cover and retard the ign. just to get home....

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My understanding is that the polyester resins are the ones reacting with the ethanol fuel.

Thankfully, I can get 0% ethanol mid grade around the corner.

One time I had to make an unorthodox repair on an OT machine. It was a H**** ATV, with low hours and daylight shining through holes in the tank. Replacement was about $600!

Cut it into 4 pieces, glassed the inside of each piece with cloth, roughed the edges with 80grit and glassed it back together with mat.

Good way to check for pinhole leaks is to paint it with cheap spray paint and fill it with gas while the paint is fresh. Where ever the paint washes away, there's your leak!
west-system is the leading product for glass work on boats google them I bet they have you're answer on their site you can probably call direct for tech support,talk to a pro...
Has anyone tried that radiator shop in New Jersey that coats tanks inside with plastic? They advertise in Walknecks.
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