How to get oil cap off without breaking it?

[bonne]

The bloke chaging the oil last time has been tightening it way too tight.

How to get it off without breaking it?

[bonne]

OK, I could use a large plier for it

[porter]

An adjustable spanner will do the trick and not mark the filler cap.

[bonne]

Yeah, OK... I used exactly this https://www.avxperten.dk/vandpumpetang/bahco-vandpumpetang-250mm-ergo.asp?gclid=CjwKCAjwi6WSBhA-EiwA6NiokxgemKjSsHCEIutxAn8K5f8NF4tkyBqWXyCLfqE8PPI9R8giZ9tspRoCHQEQAvD_BwE

Not sure about the English name... took some paper in between... and it didn't damage the cap.

[Rusty Nuts]

Gland pliers or water pump pliers are the two names that I know for that item.

[Tiggerbits]

I have a knipex plier wrench which has been used to do this among alot of other jobs on the bike as it doesn't cause damage. Maybe a bit pricey for a single job.

[sillyboy]

as said, gland nut pliers or as we know them -- hens legs.

[Joe Rocket]

Don't be fooled by tools for the job and go by your instincts bonne.

It's a solid plastic filler cap, nearly brand new, used less than a few times, not affected by sustained high engine temperatures (age), with oil below it's unlikely to seize (the casing it sits in is alloy).

Having said that I wouldn't use ordinary pliers from above just long nose pliers from the side for increased leverage. Put a wadding over the flange on the cap to avoid surface damage.

Finally clean and just tweak the cap a bit more than finger tight when replacing (like an oil filter).

[bonne]

actually oil filter has to be tightened more than finger tight according to the service manual... but that is another story

[Gert]

Its almost starting to sound like the oil cap may have been cross threaded or abnormally tightened down.  Perhaps Bonnie can snap a pix or two of the oil cap, in relation to the engine casing.
A pix can be zoomed for a clearer view, to determine if any uneven gap, where the cap stops against the casing or foreign tool mark is present.

[bonne]

I could take a pic, but I managed to get it both off and on again... it looks very normal and not ruined...

[The Doctor 46]

Dynamite! ............................... Oh sorry, I've just the original question again and noticed that you did mention, without damaging it. 

[SteveDL1K]

Ball peen hammer, Its easy smash all the casing in.
Get a pair of good knipex and nibble away at the edges and that should get your cap off with not a single scratch!

Glad you're sorted!

[purplebikeunicorn]

Its almost starting to sound like the oil cap may have been cross threaded or abnormally tightened down.  Perhaps Bonnie can snap a pix or two of the oil cap, in relation to the engine casing.
A pix can be zoomed for a clearer view, to determine if any uneven gap, where the cap stops against the casing or foreign tool mark is present.

Can confirm from my previous bike, that these plastic caps can be a right bugger to get off if tightened by a strongman. I did the same (molegrips, with some rubber in the jaws).

[The Doctor 46]

I had a Honda XR250, I've had six XR's of different sizes, anyway. The oil is in the frame and the dip stick in the middle of the upper frame in front of the tank. It's awkward to get out but a nightmare to put back in, hence, the oil only got checked once a month. Nothing to do with your problem, just saying.