paint / gas cap /pix /WTF

[Scooter33]

There was a bubble under the original paint so I had it repainted. 10 days later this is what I found. I have no idea who made the gas cap it is vented and it works but still this shit happened. I ordered a new gasket. I used jb weld and that didnt help. Thinking about experimenting with 2 part epoxy and gluing in the bung to the tank. any ideas on preventing this. This will be the 3rd and last paint job.

 

[Matt Moore]

Hi Scott,

From my experience, that is caused by a venting problem or over-fueling the tank. First, make sure that you do not fill the tank past the bottom-most part of the fuel tank bung while the bike is on its kickstand. Next, check to see if pressure is building inside your tank and escaping at the point of least-resistance--> between the bung and the tank. This usually happens when the bike is hot and is put on its kickstand shortly after fueling. Next time you get the bike hot, slowly unscrew the fuel cap and see if you hear pressure trying to escape the tank. Big Dog used two vents in their fuel tanks:
1.) Gas cap--The stock cap was a 2-piece cap. A white EPA valve was screwed into the bottom (inside tank) side of the cap. It was common for this valve to clog after a couple years and cause vaporlock/fuel starvation. If I remember correctly, this valve was a 1-way valve that only let air in...not out. The good news is it can be simply removed and 99% of the time it will correct any vaporlock issues. However, your gas cap is not stock.
2.) Inside tank vent-- Most models had a metal or rubber hose that runs up to the bottom of the bung inside the fuel tank. This allowed air to escape the tank when pressures rise. If this is your problem, you need to correct it or you will continue to bubble around your gas-cap paint saver.
Hope this helps. Cheers.
Matt

 

[Iman]

Mine had the venting problem and I also repainted 3 times. Took off the white piece and all is good now. But I'm paranoid. So after I ride my bike and park it in a garage or trailer, i take the gas cap off for a couple of hours till the bike cools down. My thinking is that the fuel is hot and starts condensating around the ring of the gas cap which causes the bubbling.

 

[Scooter33]

Thank for the reply. I have been keeping an eye on the gas fill level, may have gotten it a fuz over the sweet spot. I ran .032 welding wire through the vent tube and I think it is clear but not sure due to the tank liner peeling. The wire didn't feel like it hit the bottom of the tank.
The cap is vented but should I increase the size of the vent opening?

 

[Iman]

just blow thru the end of cap. if its clogged, you will know it. no need to make it larger if you can blow thru it

 

[ground pounder]

I have agood friend who is a painter. He said that he has tried everything you can think of to stop the paint from bubbling around that area and eventually it does that because the gas fumes get under the paint and primer. Mine did it one time after I put it in the trailer on a hot day. I cut out a stainless ring a little bigger than the bad area and siliconed it in place with special fuel resistant sealer and screwed the paint saver on and so far no more problems. Doesn't look bad either.

 

[Mr. Wright]

I made a washer to go under the paint saver that is about an inch bigger in diameter, to cover the messed up paint, and sealed it with black silicone. I have done this to several bikes, no complants from any of them.

 

[Scooter33]

It's worth a try. Where did you get the gas resistant sealer? I have the same question about the black silicone? is it RTV?
Thanks

 

[Mr. Wright]

Yes, I believe thats what it is. I don't put the o-ring back in, I just use a small bead, about as wide as the o-ring was.

 

[Mr. Wright]

NOTE: On my 03 chopper the top of the tank is fairly flat. The ones I've made for K9's had to be cupped in the back and rounded a little to fit the shape of the tank. I don't know what the top of a tank on a Mastiff looks like. Just take your time fitting and polishing.

 

[ground pounder]

Fuel resistant sealer is made by dow corning. Its silicone based.

 

[Knuckles]

NOTE: On my 03 chopper the top of the tank is fairly flat. The ones I've made for K9's had to be cupped in the back and rounded a little to fit the shape of the tank. I don't know what the top of a tank on a Mastiff looks like. Just take your time fitting and polishing.

I like the idea and looks. are you selling these?
how much for one that fits a k9?
my paint is showing first signs of a little bubbling. I guess that isn't bad for an 07 with 28k on it

 

[jimizee028]

I am a painter and painted quite a few in my time,and what I do is first off dont paint down into the bung...
second I stop my paint where the tank meets the bung,taping off the bung
Third when job is all done I run about a quarter inch seal of JB Weld where the paint meets the bung..
The paint doesnt climb under the JB Weld and I have never had a complaint and have painted all my bikes,my brothers my friends and numerous customers.......