Replacement weld bung for petcock

[fxray]

A guy I know is working on an SL350 K2 for a friend of his. The fuel tank was in pristine condition as far as the paint goes. He had some rust inside and tried to clean it out and use POR-15 liner. It sounds like he did not get the coating mixed properly and the liner failed when he put fuel in the tank (after letting the liner set up for a couple of weeks). So . . . he tried vinegar to remove the failed liner and got most of it out. Problem now is that the vinegar destroyed the petcock bung. It literally ate half of it away. I have been trying to find a replacement bung on-line but am having no luck. I am surprised to find than most weld bungs are made only with internal threads. There are a number of places that sell 22mm externally threaded weld bungs for Harleys, but he needs an M14x1.5 externally threaded weld bung. When I searched on here, the only person who mentioned a petcock bung was RockReef, and he hasn't been seen since June. Anybody else done this before?

 

[EzPete]

A guy I know is working on an SL350 K2 for a friend of his. The fuel tank was in pristine condition as far as the paint goes. He had some rust inside and tried to clean it out and use POR-15 liner. It sounds like he did not get the coating mixed properly and the liner failed when he put fuel in the tank (after letting the liner set up for a couple of weeks). So . . . he tried vinegar to remove the failed liner and got most of it out. Problem now is that the vinegar destroyed the petcock bung. It literally ate half of it away. I have been trying to find a replacement bung on-line but am having no luck. I am surprised to find than most weld bungs are made only with internal threads. There are a number of places that sell 20mm externally threaded weld bungs for Harleys, but he needs an M14x1.5 external threaded weld bung. When I searched on here, the only person who mentioned a petcock bung was RockReef, and he hasn't been seen since June. Anybody else done this before?

Maybe do the 20mm and use a petcock from a 500T? That's a 20x1.5 thread.

 

[fxray]

Maybe do the 20mm and use a petcock from a 500T? That's a 20x1.5 thread.

Sorry Pete, I made a typo in my earlier post. The Harley ones are 22mm. I have corrected my earlier post. If at all possible, he wants to keep it like the original. It may wind up being a custom made piece, but it seems like there ought to be something out there.

 

[boddy]

What if you took the coupling nut off the petcock and welded that to a steel plate. Cut out the old bung and weld the plate/nut assembly onto the repair area of the tank. The only thing to watch out for is that the nut is welded to the plate such that the petcock faces out when fully tightened.

 

[fxray]

What if you took the coupling nut off the petcock and welded that to a steel plate. Cut out the old bung and weld the plate/nut assembly onto the repair area of the tank. The only thing to watch out for is that the nut is welded to the plate such that the petcock faces out when fully tightened.

Well, I'm not sure that would work. The petcock and the tank bung have to seal end to end. The nut draws them together with LH/RH threads. I think he will need to find an actual replacement weld bung somewhere. I have an old tank with some dents in it that could be used as a donor, if the bung could be cut off my tank and then welded to the good tank. Maybe we can get a new one made on a lathe.

 

[EzPete]

Sorry Pete, I made a typo in my earlier post. The Harley ones are 22mm. I have corrected my earlier post. If at all possible, he wants to keep it like the original. It may wind up being a custom made piece, but it seems like there ought to be something out there.

Ah dang. Sounds like a custom cut job, or finding a donor tank.

That said, if the bung is already that shredded, the rest of the metal in that tank may not be far behind.

Might be time for a whole new tank.

 

[mike in idaho]

If you have access to a lathe, you can bore out the center of an appropriate sized metric bolt, then face off the end for a sealing surface.

 

[fxray]

^^^My machinist friend suggested that today as well. I think that is the plan, if it turns out that the rest of the tank is still sound enough for welding.