Tuning theories differ greatly on carbs, in the past the theory big is best with carburation is not always the case. Smaller carbs tend to promote torque and cleaner running, larger carbs tend to promote more top speed, at the expense of bottom end power. You can as with everything in life go to small or to large, either starving the engine, or flooding it, again you need a happy medium.
Many tuners of two strokes have started using simple carburettor designs of smaller diameters, as getting the jetting correct on a two stroke can be the difference between an engine performing to its full potential, or being 4 or 5 hp down on well tuned engines. In general size of carb needs to be chosen by the cc of your scooter, level of tune, the air intake system and the exhaust, not just one factor.
The most common carbs on Lambretta are Dell’Orto, both in terms of standard and bolt on performance types. But there are increasingly more and more different makes entering the market for use with Lambrettas, so again the choice is wide and varied. Many claims are always made of which carb is best, gives you most power, easiest to use etc. We have worked with Dell’Ortos for many many years, and these have proven time and time again to give the best all round results. The Dell’Orto carbs come with probably the largest selection of spares of almost any make of carb.
Standard items are for all Series 3 Lambretta machines from the SH range of Dell’Orto carburettors. Although no longer manufactured a huge amount of spares both new and second hand are still available. The smallest bore on the S3 Lambretta is the 18mm. then going up to 22. After market and bolt on carbs can go from 22 right up to 34, although you can and there are larger carbs then this, in general larger carbs tend to be too much for the humble Lambretta!
Carburettor sizes and recommendations vary from tuner to tuner, it is probably best to speak to your chosen supplier and see what they recommend. Roughly speaking
125 to 150cc keep the original carb, possibly go to a 22mm
175 (tuned) 22 to 28
200 + (tuned) 25 to 30
When the mention tuned, we mean by means of porting, exhaust, etc.
On more exotic kits such as the GT, Imola, TS1 etc, you need to follow your suppliers recommendations, as they tend to run on differing carbs.
