Oil tank cap seal

andyblue · Post by **andyblue** » Mon Nov 14, 2005 1:59 pm

Does anyone know the inner mysteries of the spring loaded thingamagig in the oil tank cap? The rubber seal is going West in the cap on my '55 18S and oil is escaping from the cap and trickling down the tank/my leg etc. There is what looks like the head of a split pin in the centre of the assembly but I can't see an obvious way to dimantle it, and it would seem that you have to take it apart to put a new rubber seal in as part of it is clamped by spring pressure.

Also I can find no reference to an oil tank cap seal in the parts list so it looks as though I will have to make my own replacement, unless someone knows any different.

Andrew

RogerNorman · Post by **RogerNorman** » Mon Nov 14, 2005 7:49 pm

I presume you are refering to the filler cap and not the filter cap although a 'spring loaded thingamagig' also exists on the top of the filter. Likleyhood is the cork washer inside the cap has flattened out and when you push the cap on it doesn't seal. You dont need to take the cap apart to put a new cork in although its a tight fit. You can soften the cork up by boiling it in water before you fit it - this makes it more pliable to allow an easier fit. You may have trouble finding a source of pre-made cork seals but a sheet of cork can usually be sourced at people like Autohose who frequent the Autojumbles. From this you can cut a new washer and fit. I have replaced corks on all of my machines recently and it does stop the 'wet leg' syndrome.

Biscuit · Post by **Biscuit** » Mon Nov 14, 2005 8:09 pm

The last clutch dome cork I received for the pressed steel chaincase had the centre still in situ, it pressed out quite easily. So far it has supplied two tank caps!!!

GSAX1 · Post by **GSAX1** » Wed Nov 16, 2005 6:56 pm

I recently "dismantled" my petrol tank cap by mistake when I pressurized it with compressed air through the went hole on the top. I tried air pressure to clear the stoppage in the (inside) vent hole, but instead the spring loaded part bent where the two indentantions are and the contents shot out! Thus I could find out how it is built up. The pin in the centre has no other function than providing anchorage for a chain. Loosening or taking out this pin will have no effect on removal of the inner assembly.

Try instead to jam one side down under one of the indentations and pry it upwards with a small screwdriver over the indentation on the other side. Don't worry if it bends slightly, you will be able to straighten it out afterwards.

When you take it apart you will notice a lot of rust and rubbish inside. Clean it out and clear any ventholes.

It sounds difficult but now that I know the technique I am able to dismantle the oil and tank caps (they are similar) without much difficulty.

You can buy new cork gaskets on eBay:
http://cgi.ebay.co.uk/NEW-CORK-2-1-2-PE ... dZViewItem

I just did and they are real good.

Hope this helps
Michael

TommoT · Post by **TommoT** » Wed Nov 16, 2005 11:16 pm

...another and more durable alternative is to buy a sheet of synthentic rubber of the correct thickness. Can't remember exactly how thick, but measure the old cork and add a bit for wear. This material has lasted in my petrol cap for 5 years without any signs of deterioration. And the best thing is that it leaves the cork for it's proper use, to seal bottles!

Cheers!

RogerNorman · Post by **RogerNorman** » Thu Nov 17, 2005 9:52 pm

Now why would you want to seal a bottle? Thought corks were for removing from bottles so you drink whatever was inside

TommoT · Post by **TommoT** » Thu Nov 17, 2005 9:59 pm

...good point, but before you can do that, it has to go in there...erhh, this begins to resemble the discussion about the hen and the egg...