Some photos and then a question

Did you try to stretch the spring?

I would also look to see if there are some hairline cracks in the rubber. A bike that old you might have to replace the rubber. Mine is cracked all over and will need to replaced before mounting the tank on the bike.

Chuck

To see if it was the spring vs. the rubber or vent I would try placing a thin plactic sheet (like from a sandwich bag) over the filler hole and close the gas cap and see if it leaks. Do not ride it like this because you blocked the vent and will not get far.

Chuck

Okay, frustration running high in my garage. I found a spring that I cut for heigth and placed in the cap along with the original spring. Tilted the bike to the right - still leaking. I placed a rubber glove over the fill neck and closed the gas cap. Tilted the bike to the right - no leak. I ordered a new cap this afternoon. I'll post the results when the cap gets here next week.

Next week if you read from California, "CRAZED MOTORCYCLE RIDER SETS FIRE TO NORTON COMMANDO IN HIS DRIVEWAY," that would be me.

Maybe you should just keep a rubber glove under the gas cap? OH, boy, I didn't say that!!!

Dave
69S

DogT said:

Maybe you should just keep a rubber glove under the gas cap? OH, boy, I didn't say that!!!

Dave
69S

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I guess I could do that, but the wind would make it wave at people as I rode down the road.

That might be cool. Maybe some girls would wave back? Don't I wish.

Dave
69S

Usually the rubber get stiff or fractured.
Some drill out the center rivet then sheet metal screw back
another seal complex, but I'm told the rubber can be pulled
out its tin center and a new one softened in hot water worked
back in.
I've not yet done this be that's my plan on two gas cap
leaks that spoil paint starting with the gas fill neck.

hobot

I gave up yesterday and ordered a new cap from Old Britts

calbigbird said:

Hey L.A.B. as long as that cap is apart, how tall is that spring? I just measured mine at .75".

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(Sorry for the delayed reply, as I missed your question)
That's an old photo, but the spring is .80".

I know you've ordered a new cap, and to answer hobot, the cap seal can be removed and refitted quite easily as even the old seal should still be relatively pliable.

As I said earlier in the thread, I fitted a new rubber from RGM for £ 1.40 - it went in without too much difficulty; I found that rotating the seal got it lined up in the groove OK.
The old one was visibly split and useless, so ripping it out was no problem :mrgreen:

I got my new fuel cap from Old Britts today and managed to get it installed without scarfing the paint on the tank. So far there is no fuel leak with the new cap on. I wouldn't think that after replacing the rubber gasked there would be too much to go wrong with a fuel cap, but something in my old cap failed. I'm keeping my fingers crossed until I get a really full tank of gas in there, but it is pretty full now and isn't leaking at all. Whew!!!!!

I'm a little late to this party, but I have another insight for the benefit of anyone who has this problem in the future.
One other thing to check is the flatness of the metal disc/flange in the cap that actually pushes down on the rubber gasket. I was having the same issues as you up until a few weeks ago when it finally occurred to me to check that out. Turns out that flange was actually bowed a bit with the highest point on the right side. The low parts of the cap at the front/back would seal just fine but the sides wouldn't push down on the gasket at all because they were too high. All it took for me was some slight bending to get it roughly flat and rotating the flange so the lowest point aligns with the right side, and no more leaks. First time I've been able to fill the tank past 2/3 full since I got the thing!