Can I play with madness?
A common carb upgrade for Vespa scooters is the Si26 fast-flow unit. The Si carb is fairly utilitarian in its design, but the 26mm fast-flow is a simple ‘like-for-like’ solution that works well to give a small performance upgrade and also supply the necessary increased fuelling demands when tuning an engine. This, however, only works if the carb is fitted correctly and accompanied by the necessary specification of other components.
A good example of what can go wrong in this situation arrived at the garage just this weekend. The chap in question, Dylan, had managed to acquire an old scooter (Piece of Mind) that formerly belonged to one of his clubmates. Its paint job and bodywork starting to show signs of age, but still intact, and very nostalgic.
Just 9bhp from a Malossi 210 MHR?
The scooter had arrived in his ownership with just a standard PX125 lump fitted, so Dylan upgraded to a P2 lump and had a Malossi 210MHR kit fitted, along with a 60mm crank, 26Si carb and a SIP3 pipe. This combination of components usually receives around 16-20bhp on my dyno, depending on how it’s built and set up.
Unfortunately, Dylan’s engine only put out a paltry 9bhp. I could
