One of the things I have been meaning to document is how the fuel caps go together as used on the Suzuki GT series between 1973 through 1975 on the GT380, GT550 and GT750. All of these come apart quite easily for re-chroming if you choose to go that route – they also are still available from Suzuki for about $117 in the USA, but if you buy a new one it will not be the same design as the earlier ones which may be important if you are doing a restoration.
The main difference between the original style and newer ones is the diameter of the release button – early ones are small and later ones are large as seen in the photo above.
Referring to the photo above, the release mechanism consists of parts 1 through 6 and is disassembled by carefully removing the two half clips (#5 from their seating positions in the retaining collars item #2. At this point, if you are not careful it will all fly apart and the small and crucially important little spring (which I only just noticed is not labelled) and other bits will disappear forever into the dark corners of your shop meaning you have no choice but to buy a new cap. If you were careful though, you will have eased it all apart and the various bits will appear as per the photo. The collars (item #2) are an insidious design being plastic and so tend to crack and fall apart quite easily. Item #7 which is a retained spring and seal may be prised out of the outside shell item #8 which can then be sent away to be chromed. Having the spring retainer out also makes it easier to replace the sealing gasket which is still available from Suzuki.
This specific cap in the photo is an early style – as mentioned the later ones had a larger diameter collar. The caps used in 1972 actually are quite similar but lack the locking buttons, using instead a release lever.
Whether you buy a new one or rebuild your old one is a personal choice as the cost is about the same, and included with a new one are new latch and hinge pins, plus a couple of keys. At the same time I also think it is nice to know that if you want to preserve the original look it is possible to do so. Enjoy !