Posa style carbs trace their history back in the late 60's early 70's and they was originally sold for aircraft use. Don't confuse the word "injector" with fuel injection 'cause they are basically flat side single needle carburetors. The first to appear was the Lake injector then came the Posa, main difference is that Posa is casting aluminum and Lake is a machined product so they soon disappeared 'cause much expensive. In the old days many drag-bikes and street racers were equipped with flat sides, nowadays they are pretty rare to find. Posas & Lakes have the nasty reputation to be tricky to be tuned but if they receive the good set up they gives neat performances.
Triumph Scrambler X-12
2 ore fa