I am not sure what the timing is set at - but if it were not set right, wouldn't the high rpm produce high HC as well?

Here are the latest numbers:

RPM @2613
HC = 81 (200 is limit)
CO = .35 (1.2 is limit)
CO2 = 14
O2 = .62

RPM @910
HC + 192 (200 is limit)
CO =.18 (1.2 is limit)
CO2 = 14
O2 = .72

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Two years ago, right after an engine rebuild, I got the following:

RPM @2444
HC = 79 (200 is limit)
CO = .55 (1.2 is limit)
CO2 = 14.2

RPM @1005
HC + 100 (200 is limit)
CO =.17 (1.2 is limit)
CO2 = 14.9
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I was expecting after a rebuilt motor to have excellent results. But the high HC at low rpm was a surprise. Before rebuild I had similar numbers. If rpm here is lower (e.g. 925), then the number is much worse.