Plastic Gas Cap Repair

[skiri251]

It is time to tap into the wealth of knowledge of this great forum again.

I was bitten by dirt bike bug a bit and bought myself the following.

She looked okay in the photo and the seller told me he only took her out around the camp ground, never heavy-duty enduro stuff.
Yeah right. Brought her home and upon close inspection, found all sorts of issues. Both front/rear rims were cracked, magneto rusted, tranny oil looked like cream stew, etc.
Ended up fully rebuilding her right now.

One of the issues is this cracked gas cap (which the seller disclosed before the purchase. LOL)

I saw NOS gas cap on eBay but that costs $69! :head bang:
I have already spent more than the bike purchase price for various parts and just don't feel like paying that much for just a gas cap.

NOW, do you think I can repiar it with some sort of glue or this fine piece of equipment from you know who?

https://www.harborfreight.com/plastic-welding-kit-80-watt-iron-67102.html

I am afraid it's not ABS...

 

[joedrum]

got to be someway to fix it ...im sure...stick expoxy or plastik weld ...abs glue something

 

[skiri251]

I don't have any luck with glue lately (not this gas cap).
They seem to be so specific to the types of plastic. Tried to repair Coleman collapsible water container cap with ABS cement. It peeled right off once dried.

I guess the welding doesn't work if the plastic is thermally hardening type...

 

[backlander]

skiri, post a picture of that cap upside down and what is the diameter of the threads, or is it a twist tab type cap?

 

[AApple]

Plastex

 

[flash2002]

Go to E-Bay, I saw one there for 13 bucks

 

[slabghost]

Maybe a hot glue gun? Or a soldering iron to weld it? Maye you can just used a jar lid?

 

[skiri251]

skiri, post a picture of that cap upside down and what is the diameter of the threads, or is it a twist tab type cap?

The pic attached.
The thread size appears to be 2.55" (65mm).

 

[skiri251]

Plastex

Hmmm.
I guess I will try this if others fail.

 

[skiri251]

Go to E-Bay, I saw one there for 13 bucks

I don't see that.
I see $30 (free shipping) one but that's not for mine (1979).
I have this incredible luck of always getting the rarest model year...

 

[skiri251]

Maybe a hot glue gun? Or a soldering iron to weld it? Maye you can just used a jar lid?

I gota hot glue gun. That's no cost for me!
I also happen to have "Seal-All" sealant/contact glue which says gas/oil resistant. Maybe that's the first choice?

 

[dan filipi]

Just a thought maybe an auto oil filler cap would fit?
Wouldn't have the venting though so maybe forget I said anything. :mrgreen:

 

[Bobo]

For whatever it's worth, for such repairs I use original JB Weld, pushing some into the crack all around, lightly clamping, then building a skin on the outside with a little fiberglas substrate. Don't remove clamp until it's fully cured. Very tough when hardened up, 24 hrs to be sure at 70 degrees +.

 

[skiri251]

Just a thought maybe an auto oil filler cap would fit?
Wouldn't have the venting though so maybe forget I said anything. :mrgreen:

If it fits, it's easier to drill a vent hole and put one way vent valve.
But I don't know where to find the cap. NAPA?

It seems there is no standard for these threads. I have couple of plastic gas containers and the caps are not interchangeable at all.

 

[skiri251]

For whatever it's worth, for such repairs I use original JB Weld, pushing some into the crack all around, lightly clamping, then building a skin on the outside with a little fiberglas substrate. Don't remove clamp until it's fully cured. Very tough when hardened up, 24 hrs to be sure at 70 degrees +.

I see. I guess JB Weld will stay in the crack even if it doesn't adhere to the plastic. Then maybe this "Seal-All" sealant will seal the rest?

 

[Bobo]

It won't just stay in the crack, it will bond it if you push enough in to reach half the depth of the crack. Remember, you're then lightly clamping it. I'd use good rubber bands if nothing else is available. Let this stage cure fully, at least 24 hours at 70 degrees min.

For the fiberglas substrate and finishing it, I would cut fiberglas mesh pieces that fit between the lobes on the cap, at least 6 of them. Apply JB Weld in a thin coat, apply the fiberglas piece til it sticks down nicely, and then coat it with a slightly thicker skim coat of JB. After about 20 minutes of curing, you can shape it in easily with light sandpaper or whatever. If you're really anal, you can make it look OEM with extra-fine sandpaper and black/charcoal spray paint, I guess.

 

[skiri251]

Okay.
Went with JB weld.
It's c-clamped now at 78 degree room temp.
Hopefully it sticks to the plastic. :beg:

 

[Bobo]

So how'd it turn out, Skiri?

 

[skiri251]

Looks okay so far. I guess I will find out when I screw the cap on.

Been busy re-building wheels. Then engine rebuild, carb rebuild, a little more way to go before the gas tank will be on the bike.
Will try it some time before that.

 

[Bobo]

You'll definitely want to reinforce the simple bond in the crack, whether the fiberglas with JB Weld skimmed below and over or the stuff you mentioned. When you tighten it all the force will be trying to break open that crack.