Ariel Owners Motorcycle Club

I am having great difficulty removing the cap. I have removed the two o rings and it is no better. It seems as though the plastic has expanded. Unless I find another explanation I intend to sand down the plastic. Any other ideas please?

The cap on my Arrow is also something of a tight fit with the 'O' rings in place.
However, without them it simply drops in. The rings are probably original and
are not that flexible and will be replaced at some stage in the hope that I won't
then need both hands to get the cap out.

I measured the setup out of interest a while ago. This is what I found:

The tank hole is 1.83".
The body of the cap is 1.79"
The 'O' ring appears to be 0.11" diameter
The 'O' ring gap is 1.63" in diameter and 0.16" wide

This gives a compression of 0.02" on the 'O' ring.

As it's the rings which make the seal reducing the OD a little shouldn't hurt.

Thanks Will for the response. Unfortunately my cap is a very tight fit without the rings.

My cap was very tight even without o-rings so I wrapped some emery cloth around it and swizzled it around in my hand until it fitted very loosely. I then put on new o-rings and all is well. I believe that the plastic swells over time.