Newbies Fuel Cap Gasket Question

I recently purchased a 1938 Primus No. 71 and purchased a gasket set, seller most likely on here. Anyway, the 16mm OD with center whole is a bit wide it seems to install in the cap without some major distortion of the gasket. See photo including very old shrunken gasket. Is there a right way to seat these, or trim it at my own risk?

 

The gasket should sit flat and neat on the inner surface of the cap. It should touch the edges of the cap without distorting.

Tony

 

Doesn't look to be one of mine (Fettlebox) but which cap do you have?

 

I actually meant to fit it you had to distort it....

 

I'm away from home where my reference measurements are but I think 16mm OD is correct for that cap. It should seat properly once pushed below the threads.

 

Will keep trying, if I get below the initial threads on one side, then the other side of the gasket seems impossible to push down.

 

Have you checked it is 16mm OD?

 

Yes, it is. May just be thicker than OEM and hence less flexible.

 

John.
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