Are piston springs an important tuning factor?
SU specified fewer than ten piston springs for all types, and for the HS type only four are suitable. SU also supplies over 600 needle profiles for the three jet orifice diameters. Obviously the fuel needle is the most important aspect of tuning for a particular engine. As long as the springs are undamaged, and equal in length, successful tuning is possible. Early SU’s, and some used into the 1950’s used no springs at all.
