Indian Enfield..... errr no I think the Honda 250 would trounce it, besides you can tune this bike easily, just swap the engine for a 500 as all mounts etc are the same
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Plan A is I have a 285cc kit and yoshi cam in my war chest for it. I wanted it to be easy to ride small bore 4 stroke as have plenty of 500s sitting about and needed a change of pace.
Like anything, if I built the KSI them bike again I could build it twice as good. It would be easy to do as a kit, you could do a nice little laser cut conversion bracket for the top shock mount and a set of instructions on where to cut and paste. Then all you need is old IT swingarm and CR detachable sub frame. With a mig welder you could do it in a day.