I am in the early stages of planning a Tracker build. It helps pass the time and keep my brain occupied while I take care of business half way around the world from home in a high, dry, landlocked place that time has forgotten. I won't call it a Street Tracker because I expect much more than that out of it. I picture one bike that does it all. From slamming canyons, to commuting, riding backcountry fire roads, a little off-road in the desert or two-up day touring with someone special. I focused on the following priorities in choosing a base motor. It must be a twin, between 600cc and 900cc, with readily available parts, have a broad strong power band, be capable of 70HP or more with a little work, be relatively lightweight, have a good track record of reliability and not be crazy expensive. To this point I am looking closely at the Aprilia 750, BMW 800, Suzuki SV650 and the venerable Yamaha XS650. None are perfect, but I think all could do the job well. I'm very interested in feedback.