ok guys im helping a friend of mine with her nightster

long story short her mom bought this bike in 2008 brand new, fell in her yard and broke her clavical.. decided that riding wasnt for her
so over the last 15 years the bike saw a total of 735 miles...

have completed all service for her including new tires/tubes/bands, brake system flush..

the issue is the gas cap.. tight coming off and extremely tight going back on i dont think she is going to be able to deal with it when she needs gas
i had an 09 nightster and i seem to remember the same issue but i cant 100% remember the fix.. i believe all i had to do was rotate the caps threads
while cupped in some sand paper..

is this it??

any help is appreciated

 

The cap on my bike and probably the same on all bikes it has a "funny" thread that on undoing goes easy and then stops and at that point requires a firm grip to turn it.

When putting on the cap it should turn reasonably easy until tight. If you continue to turn then there is a ratchet mechanism.

Is there any rust in the threads?

The HD pop up fuel cap isn't the same and is much easier to operate, IMO.

 

Ride it to your local HD dealer and pick out a shiny new gas cap. Or Amazon if you want cheap. Or spend stupid amount of time trying to fix it and then buy a new one. That’s how things go for me.

 

What I remember is that the gas caps were not designed for ethanol gasoline and swell up a little. So take some sand paper and sand it down a little, wipe it off to get any residue off, and try it until it fits. I did this to my 2015 cap when it did the same thing. Just be patient and keep sanding until it fits like it should.

 

I had the same problem on my 92 FLHS. I sprayed the threads of the cap with graphite lube a couple of times- it smoothed things out and made it easier to remove. Probably not a permanent solution, but cheap and effective.

 

Seems as if anytime there any fuel/ fuel system related issue one guy always has to point the finger at ethanol.

I have a hard time believing that HD wouldn't have ethanol safe fuel tank components considering that ethanol in gasoline was required by 1990, and by 2005 the minimum amount of 10% ethanol was required by the renewable fuel standard. Also with the very little exposure of ethanol to the gas cap on a 2008 bike with less than 800mi on it, I have a real hard time thinking that this issue would be related to ethanol. I would point to just a bad molding of the plastic or a thread issue like improper stamping of the fuel neck/filler insert threads in the tank.

 

yes this is what im thinking was recommended and i did last time... couple quick twists on the threads of the cap in a sheet of sand paper and i didnt have any more issues
.. just wanted to confirm ..

 

LOLOL yeah no stupid repair time.. as i said i asked on here probably 14 years ago and was told to wrap threads in sand paper and give the cap a few twists
that was all that was required and no more issues with the cap

 

no rust in the threads and everything is clean, for some reason i think maybe that had a bad run of caps or tank threads werent right
and all it took was a few twists of sandpaper on the threads..

 

There is a thin tube on the inside of the filler neck, sometimes the tube can be bent outwards towards the inner wall of the filler neck and it can foul the inside of the filler caps wall. If that is the case, bend the tube slightly inwards to avoid it from fouling the inner wall of the filler cap.

That happened to my Iron 883's filler neck, I bent the tube in slightly and I haven't had a problem installing the filler cap since.