LCGB Forums

I believe with a 4 stroke engine a less restricted air filer can improve performance and MPG. What about Lambretta engines? I am mainly thinking about 22mm carbs, and putting a better filter on rather that the standard paper one.

If I were ever to run a carb that received an adequate/unrestricted airflow via the OEM hose & box, I'd definitely construct a 'sock' from proprietary filter foam. I have done a fair amount of work with figuring out how a larger choke carburettor (up to 34 mm) can run well with dry foam filters & the next development will be to construct a filter enclosure fed with outside, cooler air, hopefully via the existing 50 mm frame hole. I am firmly in the camp that doesn't think making holes in the filter box is a good idea. I tried it in the 70's & experienced heat seizures

It's not just the filter, but the air box and the hose.

I'm a fan of mild tunes with plenty of low down power and I'm running wide neck or modified (Ø50mm OD) airboxes, BGM mesh filters and BGM Armadillo/Cobra hoses on few of my Lambrettas. I don't like the idea of warm, dirty air from the under the panels, so prefer to modify the neck rather than drill the air box.

Looks factory, but rides better

I think that as the OP is interested in improving the filtration to a 22 mm OEM Dell'Orto generic carburettor, the OEM hose & airbox should be adequate, but once a certain larger size of choke is reached, then they will become restrictive. That said, it is my belief that some makes of carburettor are more 'filter friendly' than others &, of course, a free flowing exhaust will affect the adequacy of the whole inlet arrangement. An Indian alloy 175 barrel that I fettled with only a 26 mm choke couldn't run properly with an expansion chamber with the OEM filter & hose, or, indeed, with just the hose & no filter. With a DIY large elbow topped with a DIY foam filter it truly realised it's potential.

It would be interesting to see what the difference between the Italian air box/ filted and hose compare to the Spanish toolbox one if there's any advantage of either