Topic: H/A 900 kit compression ratio and cam options

[Turbogrimace]

Here’s some AH 900 pistons that I ran from 2009 to 2020, I’m sure already had some history. Broke a ring and replaced with a 836. From personal experience, there is definitely a difference in torque, with or without a cam.

Thanks for the insight. What cam did you run with the 900? Did you have any bottom end work done?

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In the 70s I had HA 900 with KH d grind cam, stock rods, used to rev the crap out it without issue. More recently the the HA 900 had a KH f grind cam, stock rods, but rarely went to red line. In the 70s I bought a K1 with the HA900 already in it, stock cam and exhaust, noticeable power difference when the bigger cam was added.

i

The d grind is milder than the f. Both have a good bit of duration. Did you notice any loss of low end torque between those two cams and compared to running a stock cam?

[scottly]

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.
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!! ) 

[willbird]

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.
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!! )

Those years add up quick :-).

When people wax poetic about recycling I think most of us riding these bikes that the mfg intended to be a 5-7 year throwaway device are a good example of recycling. If you keep right on using something that is still good you are recycling as you go :-).