Here’s some AH 900 pistons that I ran from 2009 to 2020, I’m sure already had some history.
Looks there was a wee bit of piston-to-valve interference there.
![Wink ;)](http://forums.sohc4.net/Smileys/default/wink.gif)
My 836 came to me with what were later determined to be TRW pistons, with crescent-shaped indentations from the exhaust valves, with only .310" or so valve lift from a mystery re-ground cam. (Visible at about 6:30 in the pic.) Once identified as TRW, Big Jay told me they always had to machine clearance on the exhaust side of those pistons. I don't know what compression they are, but an NOS 64mm piston with an advertised 10.25:1 has a much lower "dome". With a stock K1 head and Weber carbs with 30mm chokes, this motor still makes 70-71 HP on the dyno, after 45 years. A ported head with no other changes would bump it up over 80.
(Wow, I just realized the piston pic was taken almost exactly 45 years ago!! By the end of June, 1979, I was on a 3500 mile roadtrip on my freshly re-assembled Honda!!
![Grin ;D](http://forums.sohc4.net/Smileys/default/grin.gif)
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