Solex carbs are about the easiest carbs you will ever find, If its failed its mot on been to fast then they are moaning on about emissions, Its the airscrew you need to be screwing in, to stop air from getting in, and out for more air, look at the manual look for the air intake idle screw and the main idle screw, Also make sure your acclerator cable is correctley fitted and isnt to tight, Which will rev the engine as well,
Ian Mechanic
October 2009