Honda XL Forum

WARNING-DO NOT BUY THE LOCKING FUEL CAP IN THE LINK!!!

https://www.ebay.co.uk/itm/115611443219

I bought it for £11.50 with free postage, but it's too small.

However, I sent the diameter of the original cap to the seller (57mm) and he posted a replacement cap which fits perfectly (part number 749536). It also has a way of connecting the breather tube into the side of the cap.

I guess these caps are made in China, and so you'll be able to find a supplier on German eBay who has the correct part number in stock if you wanted to buy one.