The first road tests were to jet the Delorto VSH 34mm carb, it was very obvious when I first took it out on the road that the carb set up was far too rich and needed leaning off. With that done the next step was to find out if the cooling system chosen was working. Too much cooling with out thermostatic valve would mean the engine would never get up to a reasonable temperature and too little cooling would result in the engine boiling over. To judge this I not only connected the standard thermocoupler which is at the top of the head which is the hottest location but also connected a second one to the system just before the water returns back into the barrel which should be the coolest point, the difference between the two gives an accurate account of how much heat the radiator is able to shed. Initial signs were that it was cooling too much but it later became clear that the position of the radiator mounted on a front rack on the leg shields along with the carburetion still being on the safe rich side was the reason for the low running temperatures. Once the radiator was mounted in the purpose made under legshield scoop and the carb was leaned off even more the running temperatures were where we wanted them. The radiator scoop threw up a problem though, it was acting like a huge airbrake creating a lot of drag but it also created downforce which kept the Lambretta much more stable at high speeds. The solution was to drill holes in the scoop to allow air to pass through with out being trapped, this reduced drag and didn’t noticeably reduce downforce at high speed.
