Motorcycle CV carbs have an idle circuit, a main jet, and an emulsifying chamber in the discharge tube, on an SU it is all done by the needle. This gives poor atomization and makes them a dirty carb as far as emissions go...and why we don't see them anymore. SU wouldn't allow Triumph to use the SU on their Triumph 2000 (don't know why, the TR's had SU's, so maybe just a supply issue) So they got Stromberg to make them a copy of the SU. The series of carbs by Red Edmonton, the Lectron being the most famous, are like the SU, with the needle doing everything, no idle circuit, no main jet, and no emulsifying chamber.