Eric Buell is an admirable guy. Europe and Japan had sports bikes, but the US none. He tried to make an all US sports bike with US components, but the only suitable engine he could find was a HD sportsters engine, dating back to 1953 with flat heads, and to 1957 with OHV heads (Kawasaki 4s OHC date back to 1972). This 1957 HD engine is basically what Buells had (the Blast, was 1/2 that engine)
This old HD engines were very undersquare, with very long strokes, harking back to the days of flat heads, good for low RPM torque (like diesel engines), but not good for high performance. They also had 45 degrees, not 90 (like Ducatis, or Guzzis), or 180 (Like BMWs) where twins are smoothest..so the HDs vibrate most than most without rubber or balance shafts....although not as bad as big vertical twins w/out trickery.
Worse yet, they have a system where one piston conrod wraps the other one on the same plane (fork & blade), this makes for a very narrow engine, but one cylinder is exactly behind the other one, and thus does not get good air cooling. OK on a low performance Sportster, but Buel found that hotrodding the engine to make more power, made rear cylinder unacceptable hot, thus he devised a fan and a thermostat to keep rear cylinder cool enough.
.....interesting historical motorcycle... the Buell, ....I'd keep the Kawi, and get the Buell as a curiosity, ....but not as only bike.........only my opinion..