I have a 1974 commando 850 and had to replace the gas tank, I got one from India, gas leaked between the gas cap and tank neck, the neck was not flat, i filled in the low areas with fuel resistant JBWeld and filed it flat to get a good seal...think twice before getting a tank from india, not to go into a long story, unless you have fabricating abilities than stay away from them, that being said if you have a gas leak at the neck just make sure the neck is level, check with a straight edge on the neck and put a flashlight on the other side and see if you can see light , hope this helps with any leaks
Gas cap leaks
- Thread starter philroc7
- Start date
- Status
- Joined
- Mar 7, 2020
- Messages
- 3,156
Some cheap tanks have no internal baffling either, which only exacerbates the problem...
Onder
VIP MEMBER
- Joined
- May 11, 2010
- Messages
- 4,290
My genuine 850 Interstate tank leaks at the seal. Bought another seal. The last time I filled up the seal escaped
from the cap! I wormed it back in but hey. And it was from Andover too so you would hope they keep an eye on quality. I
am beginning to feel that quality is no longer on offer anywhere for anything.
Just a crabby old man I am.
from the cap! I wormed it back in but hey. And it was from Andover too so you would hope they keep an eye on quality. I
am beginning to feel that quality is no longer on offer anywhere for anything.
Just a crabby old man I am.
Tornado
VIP MEMBER
- Joined
- Dec 5, 2017
- Messages
- 4,956
If you have an original cap, then it is not just the seal that needs attention. Under the spring loaded sealing plate is a short bit of rubber hose. It is this hose that makes the sealing pressure, not the spring. Original rubber will be hardened from age and fuel exposure. If your plate is held by rivet, it can be easily drilled out to get at the rubber hose to replace. Use some modern fuel rated hose. Refit the plate with machine screw or bolt. This sorted my seal leaks completely.
- Joined
- Nov 11, 2013
- Messages
- 5,403
I had two seals from AN that warped from new a few years ago. Ruined the finish on my tank. Turns out their supplier used the wrong material. A recent seal seems to have worked.
- Joined
- Aug 8, 2005
- Messages
- 2,853
I use to have a leak at the cap/ filler mouth. I changed the gasket and still no joy. (Original OEM gas tank). WTF so I got resourceful.
I added another gasket sandwiched between the cap seal and the filler mouth and never had a problem of leaking since. I fill my interstate right up to the brim. You need to be wary or winds blowing the loose seal away at your fill up locations. Other than that...
no problems.
Cheers,
Tom
I added another gasket sandwiched between the cap seal and the filler mouth and never had a problem of leaking since. I fill my interstate right up to the brim. You need to be wary or winds blowing the loose seal away at your fill up locations. Other than that...
no problems.
Cheers,
Tom
- Joined
- Dec 28, 2009
- Messages
- 5,467
My MK 111 cap leaks if it's full , so I will try this after the riding season. Thanks.
My original roadster tank leaks out of the locking key hole would this stop this ?
Tornado
VIP MEMBER
- Joined
- Dec 5, 2017
- Messages
- 4,956
Well the point of tbe rubber hose is to provide a firm seal of the rubber ring to tank neck. If the is good, there should be no fuel reaching anywhere above the seal plate. Not sure how the keyed types work, but should not have an opening to the sealed side of plate I'd think.
See this post in older thread where I linked to a Lotus forum thread on exact same type of cap:
Gas Cap rubber tube inside spring?
The gas caps for Commandos have a rigid rubber tube about 1/2" long that fits inside the spring. On the replacement cap this does not compress and there is no way to get the cap down enough to latch. I removed it and the cap still seems to seal well with the spring force alone. Question is what...
www.accessnorton.com
- Status
