just an update for you regulars - I did finish the HC piston last Friday. Test rode local gravel roads on Saturday to break it in. She ran a good bit hotter, hopefully it settles down a little as it breaks in but I'll probably be putting a KTM fan on the oil cooler. first impressions: I did feel an improvement in the throttle response and believe it was a little smoother. I was neither overwhelmed nor underwhelmed by the increases in power. It's definitely snappier but I kind of expected more. For the $200-ish cost of the DIY upgrade it wasn't bad. Further testing on the trail will be needed to get a better idea of the power and heat tradeoffs. Before doing the piston change, I believe I read somewhere on the web where someone compared the change as similar to the gains felt with the pumper carb. I think I would agree with that. I did have pinging at low RPM loads. Down where she used to tractor, she now pings. I had a half tank of regular gas and attempted to put some premium in it at the station. But the local pumps only have one handle for three grades so by the time you select and pay for 1.5gallons of premium, I bet I was lucky to get .5gallon of premium in the tank. I will probably fiddle-fart around with the carb jetting some more to see if I'm still in the sweet spot.