1999 Ski-Doo Factory Shop Manual Volume Two, Page 191Get this manual
Subsection 11
Section 04 ENGINE (CARBURETOR AND FUEL PUMP)
AIR PUMP OPERATION
The DPM manifold consists of tubesDepending on the mode, the upper tube (distribution gallery) distributes pump pressure or vacuum to each bowl through hosesThe passage is then opened by the enrichment or the compensation solenoid, depending on the modeThe lower tube (vacuum collector) receives the vacuum created by each carburetor within the needle jet air inletAn air jet (manifold air jet) also allows the atmospheric pressure to enter3 12
A06C3WA
TYPICAL 1Regulator 2Pump
Air pump supplies the distribution gallery through unique hosePump diaphragm is activated by the alternating pressurevacuum within the engine crankcaseTwo hoses connect the crankcase (cylinders nos1 and 2) to the pumpA regulator within the pump stabilizes the pump pressureSince the pump pressure is insufficient upon starting, the regulator is fed directly by the crankcase pressure