Sportster based. I had one similar, it wasn't a true XR, just a look alike; '74 Sportster engine, I had the starter hump removed and welded up, Mert Lawill frame, XR hubs, gold anodized rims with stainless spokes, XR tank/seat combo, Marzocchi forks, Red Wig shocks. It looked good but was not much on performance.