Don't call me an expert by any means, but, some Honda Shadow engines are single-pin crank, and some are double-pin crank. The Shadow Spirit, and Sabre are a couple of double-pin crank models and they are said to be very smooth. The Honda Shadow Aero 1999 and older was single-pin crank, and to my knowledge, your bike is also a single-pin crank bike. I am not sure of the exact definition, but a single-pin crank bike will be much more rough as you can feel it shake like a Harley. Anyway, it could be more than this, but I have a felling that is a big part of it. Let us know what you find out.
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