I bought an NOS inner fork tube on eBay. The seller described it as an inner fork tube for XS2(72) and TX(73) and had the correct Yamaha part number (although it was written on a piece of tape stuck to the tube). Since he had the p/n I assumed it was right. When I got it, it's 36mm! It looks just like my stock '73 tubes just thicker. It's not a '77-up tube as those are 35mm. Anyone know what bike it could be for? It is 23" long. Thanks