So this is what I thought. I see lots of posts about ‘big bore’ & ‘high compression’ kits for the 650, and I wonder if any of those parts have had any attempts at matching the weight of the parts they replace.
I put the high compression pistons in my bike and there was no difference in the vibration from the stock pistons, which was very slight in the left grip causing a tendency for my hand to tingle a bit. Wrenchjockie weighed the HC pistons and they were virtually identical.
My tuner however was able to tune each cylinder separately, they were different, and that completely eliminated even the very slight buzz I felt in my left hand. Now it's glass smooth, no vibes anywhere in the power band.