[PDF] REV Tuning Manual 120302 - mikuni Tuning the HSR42/45/48 Carburetors Your Mikuni HSR comes from the factory with the tuning parts we found to work with the great majority of engine performance modifications. However, the large number of differing after market exhaust and air cleaner systems makes it virtually Joe Minton Mikuni HSR42 setup/tuning recommendations May 06, 2018The kit is called the Mikuni Mileage Kit and there are separate kits for the HSR42 and 45 carburetors because the needles are different. The kits come with simple installation and tuning instructions. Adjustments (See The Manual For Details): 1. Adjust the accelerator starting point so that the pump starts working immediately.