The early 600cc engine featured the Solex B2821C downdraught carburettor, later giving way to a Zenith. Once again I was lucky enough to have two Solex kicking around, but they were in a terrible state. Since stripping and cleaning was going to involve sourcing all sorts of tiny bits I decided to get someone else to do this, and set the carbs up. I thought it would be a good idea to have a spare so both were sent off to Gower & Lee for chemical dipping, stripping and rebuilding. They came back immaculate and ready to fit. Throttle control on the 3/25 is by means of linked rods with a spring at the pedal end controlling the return. 21/09/2013
The fuel pump system is mechanically driven by the engine. An AC design is used and, once again, I had a couple of different versions to choose from. Looking at publicity for the early 600cc engine, it came fitted with a dome type with an integral filter mesh and friction type fittings for the in and out flows. I found a NOS one on line and fitted a neoprene diaphragm to help with the effects of ethanol. Sourcing a neoprene diaphragm took considerable effort. All done and ready to fit, although we will revisit this fuel pump later as disaster was narrowly avoided by its failure.
