Small hole in fuel tank - repairable?

[Husker Red]

I made a big mistake. I was working on my bike and removed the tupperware and fuel tank. Where the glove box attaches to the fuel tank and air snorkle the embedded nut has pulled out of the plastic tip of the fuel tank. That nut is in a thin (1 cm) tab of the fuel tank which I foolishly assumed was solid plastic. Because the nut had come out, I thought I would just put a screw through that hole into the plastic to keep the air snorkle and glove box in place. A small trickle of fuel is now leaking there. Clearly I'm a fool, but I never thought there would be fuel in that thin tip of the tank. With that embedded nut pulled out, the hole was already about 2/3 of the way through that plastic fin. I am still surprised there is fuel in there.

 

So... Obviously, I feel really stupid. Is there any hope of sealing that leak with an epoxy of some sort, or should I just take my licks and buy a new (used) tank?

 

Mike

[Ken H.]

Well it's a long shot, but here is what I think I would try... Get a flat head self tapping screw, and a thick rubber washer that has a center hole the size of the screw shank and outside diameter the somewhat bigger than the screw head. Without the glove box in place screw that tightly into the spot. Abandon the location as a place to attach the bike. The box will be fine without it. Screw the air snorkel to just the box some other way.

 

I don't think any type of epoxy patch is going to do it in the long run.

[UberXY]

try J&B Weld two part epoxy, at your own risk. you would be surprised at how many race cars have leaks plugged with this stuff. There are also gas tank hole fixer epoxys that you can buy at most auto parts stores.

[bigboy]

HI MIKE

In uk we use a 2 part epoxy system called petro patch 50/50 mix , if you can get it state side it will do the job no problem. carefully press it into the hole then put the screw and nut into the oetro patch , withdraw the nut straight away and leave to dry for about 30 mins /1 hour.

carefully clean any petro patch from inside the nut and know you can reuse the fixing aswell. also if available use 3m chemical metal that,s another good one and they are obviously chemical resistant. Cheer up accidents can happen thats what the dalec said when he jumped off the dustbin (or so i am told) It can happen to anyone it,s just a pain when it does happen .

 

regards

derek

STAY UPRIGHT AND A HAPPY NEW YEAR FROM UK

[ShovelStrokeEd]

A small refinement on Ken's idea would be to use an O-ring, Buna is compatable with both gasoline and alcohol and is more or less the standard material you will find at your local Home Depot, etc.

 

O-ring size numbers more or less parallel screw sizes for the smaller ones. An O-ring sized -009 or so should work with a size #8 self tapping screw. -010 has an ID of right around 1/4".

 

If you can reach in through the fuel filler hole to get to the back side, another O-ring under a deformed thread, don't use elastic, stop nut should improve the seal even more. You would, of course, then have to use some form of conventional cap screw. A nice, stainless button head would look trick and confound the next mechanic to get in there

[Husker Red]

Thanks for all the great suggestions. Since the hole is through a fairly thin area and I have access to both sides, I think the o-ring and screw idea will work. (Possibly drill a small hole all the way through and then use a small nut and bolt with the O-rings?) I'll probably use the 2-part sealant around the screw too. Here's a photo of the problem. It is leaking through both sides. Tomorrow I'll get supplies and give it a try.

 

Thanks for the quick help!

 

[motorrod]

Mike,

 

Here's another option to consider. It's been a while since I've had the tank off mine, but I believe the tank is a rotationally molded Polyethelene plastic. At least it looks and feels that way. If so, this should be easily fixed using the plastic welding process. A google search should reveal lots of detail. It is used routinely for joining large pieces of plastic together. A prime example is for making tanks for plating lines. But I digress... A plastic sheet supplier in your area should be able to steer you to someone with this capability. It is not an expensive technology.

 

While I have used products like JB Weld with excellent success, I always worry about sticking things together with dissimilar materials. These things have a way of failing at the worst possible moment.

 

Good luck.

[ShovelStrokeEd]

Bigger can of worms there as pressure from the bolt will cause the tank to collapse. Best bet might be to upend the thing and use one of the chemical methods. I thought it was just through one surface. For the O-ring thing to work in that situation, you'll need to support the interior of the walls with some sort of blocking. Major PITA to get a block in there and then drill through all. I suppose you could do it by removing the filler neck or maybe the fuel pump mounting plate.

 

Bummer.

[flatbutt]

Since it is in the closed end tip and occupies a very small volume, how about filling the tip completely with the JB or other resistant material? Then you could drill thru it and remount as per spec. Maybe inject the goo with a small syring thru the drilled hole? Or should I just go back to sipping my scotch?

[AviP]

...I believe the tank is a rotationally molded Polyethelene plastic. At least it looks and feels that way...

Very amusing in a positive way.

 

Having no experience with plastic welding, I'd play devil's advocate and ask about what would happen if it fails. Fuel in the vicinity of a hot engine or exhaust pipe is big trouble. With all the vibrations on a motorcycle, would the above suggestions hold up. After all, there are a lot of disclaimers.

[FlyingFinn]

Here's another vote for "plastic welding".

The key is, you need to first be sure of the type of plastic used for the gas tank. With correct methods and materials applied the fix should just as good as "virgin" plastic right next to it.

 

The problem with a "screw + nut + 2x o-ring" is that the o-ring under the nut will not seal the threads of the nut.

IF you go that route you must use thread sealant on the screw/nut.

 

--

Mikko

[henryj7]

Mike,

If you can get at that spot from the inside the tank I would drain the tank and clean that area with alcohol inside and out. Get some fuel tank epoxy (JB weld should work). Fill a syringe full of epoxy and totally fill that area inside the tank with epoxy. You could probably now re-drill and tap that area or put the insert back in while it hardens.

Just my two cents.

Henry

[No_Twilight]

I would drill a 3/8" hold all the way through and make a 3/8" diameter bolt/nut out of brass on my lathe and then thread the center of it to accept your tupperware screw. Buy making them myself I could put a blind female thread on the inside so I wouldn't have to worry about leakage along the threads of the nut. Then I'd put o-rings under each side. I'd put some jbweld inside the tank in that area so fill it up to support the clamping force. I'd screw it together with loctite 242 to keep the threads from coming loose. If metric works better for you replace 3/8" with 10mm. Cheers, Jerry

[2wheelterry]

If it was my tank, I'd also look into plastic welding. Some calls to local shops may yield some results. IMHO this has the greatest chance at getting you back to where you started without risk of leakage down the road.

 

If that doesn't play out, injecting a plastic repair compound using a syringe to fill the cavity would be another option to research. Doing a Google search on plastic repair "fuel tank" did show one product that claims to repair plastic fuel tanks for RV's. Plastic tanks are now not that uncommon, my last truck, a 1996 Dodge had one, so possibly some repair methods have been developed.

 

One last idea for a solution. I remember reading about a guy who added an auxiliary fuel tank to his bike for the long distance stuff. He drilled and tapped his plastic (RT?) tank to drain the aux. tank into it. If you can find something similar, and learn what process was used, it might be helpful. I’d start with a Google search.

 

If it were mine, after the repair is done/cured I’d feel better if it passed a SMALL magnitude, controlled pressure test maybe using the vent from the tank that feeds the charcoal canister.

 

Good luck, I’ve put myself in similar shoes many times. Someone once told me a measure of a good craftsman is how well he/she can cover/repair/hide their mistakes.

[Husker Red]

Follow-up: I emptied the tank and drilled completely through both sides of the hole. The plastic there is almost solid. There is about 1/8" inch of hollow tank, but certainly enough to cause me these problems.

 

I was worried that the plastic gas tank epoxy that I bought would not work on the tank because I thought it was polyproplyne. However, I found the markings PA6 on the tank, which I googled to find is a type of thermoplastic Nylon. I scuffed the area with coarse sandpaper and even used a very rough file to scuff it more. Alcohol to clean all around it. I then pushed the epoxy putty into the hole to fill the gap. I quickly inserted a tight fitting stainless steel bolt with a viton o-ring on both sides and snugged them down and used red loc-tight on the nut. Then I prepared more epoxy and covered everything within 2 inches of the holes. Dried for 24 hours.

 

Last night I put the tank back on and tested it, then took the bike for a quick ride. So far so good. I'll keep the tupperware off for a few days to keep checking for leaks. It looks like I fixed it with bubble gum, but if it works I don't care! If it starts leaking I'll post that so others can avoid this method.

 

Many thanks to all for the excellent advice. This board has been very very good to me!

 

Mike