Can anybody please tell how to determine the difference between an early and late Dyna gas tank bung? Nobody has been able to answer specifically what the difference is. The reason I need to know is that I have a custom dash on my Dyna and a 1998 tank and yet both a 1998 gas cap and an early 1996 gas cap thread in and seems to tighten down fine. But what I cannot tell is if the pitch on the threads might be different such that the cap will not tighten down completely flat and make a good seal. I cannot see around the bung to determine if this is the case because of the dash. I don't want an unseen vapor or gas leak to slowly damage the paint under the dash panel that I cannot see until its too late. One person said if the cap screws in it will be fine, anothers says they (think?) the pitch between the two was different and they would both screw in but only one would seal and yet still another said nope....if its the wrong cap it just plain won't screw in...if it screws down it will seal? How am I going to figure out whats right? Does anybody here know for sure? I really want to use whats labled as the early 96 cap as its the only black texture pop up I can find. Maybe MudPuddle knows?? You seem to be the one with some of the most knowlege about these odd things here? Again, my dash allows the gas cap and bung to be recessed down and one cannot see the actual bottom of the cap and associated tank bung seal. If I shake the tank up good and then remove the cap obviously it will be wet around the bung so I can't tell in that manner if its not sealing or just running off the cap after being shaken up. Thanks for some concrete advice. Rick

 

If you removed your dash, would you be able tell if the gas cap tightens down like it should?

 

That would be too easy! Actually, the custom dash is pretty complicated to take off. Thats what I will have to do if I can't get an answer by somebody that knows for sure? I am hoping that its just a matter of if it screws in its ok if it doesn't its not?

 

The difference is in how the gas cap seals to the bung. E96 and earlier had a lip around the bung with a flat surface and the caps had a flat gasket which mated to that surface. L96 and on the bung is flush with the surface of the tank and the cap is sealed with basically an o-ring type of gasket.

 

Hey thanks. I guess the problem must lie then just with the Dyna FXD? It does have the raised bung thats not flush with the tank. It sticks up about 1/2" center top of the tank.

 

No, the bungs were pretty much universal, except for the touring models with the gas cap in the center console so it's not just a dyna thing. My 88 FXR had the raised mating surface, my wife's 98 Softail stock tanks don't. It's a year thing, not a model thing.

Edit: In your case, since you have a 98 tank you should use L96 and later gas caps. The E96 and earlier will screw in, pitch is identical, but it will not properly seal and gas may leak out.

 

I'm pretty confused. The 98 tank I have does indeed have the raised mating surface. The gasket on the 98 cap I bought for the dyna as well as the early 96 are both flat? I do know the softail with the caps off to the side have the round gaskets are are flush as I've seen many. The FXD I am refering to does have a raised fill bung center which protrudes just below the surface of the dash. Below that is the gas gauge. What am I missing? I wish I had a picture of the tank. I'm going to poke around Feabay and maybe I can find a pic and post.

 

This is a pretty poor picture but I think you can see the raised bung. Its raised almost 1/2" on my FXD and on this tank as well yet its hard to see.


http://cgi.ebay.com/ebaymotors/GAS-T...=p4506.c0.m245

 

Oh, you've got one of the dyna tanks with the cap in the middle, in the console. I was talking about standard tanks with the dual cap system. I have no idea what caps work on that kind of tank.

Sorry for the confusion.

 

No, thanks for the help.