Oil Tank Cap Seal

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Mart UK

Mart UK

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Hi, now I'm getting some time on my Mk3, I'm tracing an oil leak at the back of the oil tank. I think I've narrowed it down to a very tired cork washer on the tank cap. Before I replace it, do they work, is there a better way to seal the cap?

Thanks.
 
L.A.B. said:
Well, mine works but are you screwing the cap down and not just 'latching' it?
Click to expand...
I wouldn't say I'm screwing it down. I push it down slightly, turn to get past the small ramp in the cap, then perhaps a further 1/4 of a turn it comes to a hard stop. I don't turn it beyond that stop. There is a very slight up and down movement at that point. It will only turn counter-clockwise if I push down again to undo it to pass the ramp.

Am I doing wrong?
 
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Mart UK said:
Your edit: I push it down slightly, turn to get past the small ramp in the cap,
Click to expand...

My cap needs to be pushed down and rotated clockwise by approximately 30 degrees to latch, at which point there is still up and down movement.

Mart UK said:
Your edit: then perhaps a further 1/4 of a turn it comes to a hard stop. I don't turn it beyond that stop. There is slight up and down movement at that point. Like it is sprung upwards.
Click to expand...

Pushing and then turning the cap about another 60 degrees clockwise without forcing it, locks it down tight with no up and down movement.
 
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I go to cork or synthetic cork for leaks that defy the usual paper and goop sealers.

My Atlas oil and fuel caps have been renewed with 1/16" synthetic cork. In the case of the oil cap, my first try to stop a weep was 1/16" neoprene which failed.

If gasket thickness is a factor, 1/32" cork is available, and will compress to about 50% with moderate clamp force.

Slick
 
I cut out and installed one because of leaking 3 months ago. No problem there.

Now I have to encourage another leak, which is becoming difficult, so I've something to do.
 
Mine was troublesome I eventually put an o ring the same size of the tank filler on first then put the cap on, I can blow air through the overflow and pressurise the tank , something I could never do before,and now it never leaks
 
Mart UK said:
Hi, now I'm getting some time on my Mk3, I'm tracing an oil leak at the back of the oil tank. I think I've narrowed it down to a very tired cork washer on the tank cap. Before I replace it, do they work, is there a better way to seal the cap?

Thanks.
Click to expand...
These gaskets work great , i first purchased the rocker cover gaskets which are reusable and recently purchased the oil tank gasket for my MKIII ...no leaks.
A bit pricey but they work. https://realgaskets.com/product-category/motorcycle/norton/
 
Following this thread with interest due to related issue: leaking petrol tank snap cap. New neoprene no joy. I guess next will be cork and it that fails I had thought about an o-ring however annoying that would be. Sick and tired of a mess on the side of the tank to say naught about what it does to the vinyl decal.
 
I've always found cork to be effective in this application.
Mind you, I've also had good results with neoprene on the rocker covers and (horror of horrors!).. the gearbox!!
 
Onder said:
Following this thread with interest due to related issue: leaking petrol tank snap cap. New neoprene no joy. I guess next will be cork and it that fails I had thought about an o-ring however annoying that would be. Sick and tired of a mess on the side of the tank to say naught about what it does to the vinyl decal.
Click to expand...
I have had several new AN petrol cap lid seals warp and fail within days of install. They acknowledged that the material wasn't to spec. And not ethanol related.

All quiet from them when shown the damaging results to the tank and asked about compensation.
 
There was another thread regarding oil cap seal recently.

www.accessnorton.com

Oil cap seal

Anyone having oil cap leakage? My cork seal was leaking and the leak stopped when I changed to a silicone washer. Anyone else interested in making this conversion?
www.accessnorton.com www.accessnorton.com

Perhaps info there may help.

Slick
 
After using their rocker cover gaskets with great satisfaction I had forgotten about them.... So did fuel cap & oil tank for neatness sake. Thanks for the reminder.
 
Torontonian said:
Are you running a breather reed valve ?
Click to expand...
The breather is a non-standard routing along the left swingarm. IDK if it's a red valve arrangement. I'll check the routing to see if it might be causing pressure.

Did 175 miles today, with a group of mates on modern bikes. The Commando kept up fine, handled really impressively. I'll have to sort the bushing to raise my sidestand, to stop it scraping!

Oil out the back right, up to the oil tank cap. So will look at the options posted. Also, I think (hope) my tacho drive is leaking. But I've sorted the primary weep (LAB's suggestion of grease on the gasket faces is holding up) and the rocker covers are now good. Steadily work through it!

Thanks.
 
Mart UK said:
Also, I think (hope) my tacho drive is leaking.
Click to expand...
There is a fix for that by machining the drive housing and replacing the o-ring with a real oil seal. First appeared in a Norton Tech Digest years ago, now the upgraded housing is available directly from suppliers:

https://andover-norton.co.uk/en/sho...-drive-housing-with-oil-seal-06-1090-06-5200-

1619284698384.png


That was the first place my bike started leaking from, only one year old. I was on a weekend holiday ride a few hundred miles from home and my right boot was covered in oil. Boo.
 
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