BOMBARDIER 1996 Ski-doo MX Z440 Handbook page 192

Section 04 ENGINE PREPARATION
APPLICATION
The carburetors must be adapted for use with the H.A.C. There must be a connection to provide
venturi pressure and the air jet main opening is plugged. A small hole is drilled into the top of the
air jet passageway. 1994 models use much richer carburetor jets because the H.A.C. is providing
reduced float bowl pressures (thus leaner mixtures) at all temperatures and altitudes.
Example :
Main Jet
Needle jet
Pilot jet
The vent tube on connection 3 is routed to the atmosphere below the carburetors. This is to help
prevent snowdust ingestion, and provides a drain for any excess fuel in the system from a machine
tip over.
The system is very sensative to air screw adjustments. 1/8 turn will have a large effect on low
speed tuning. The system responds to other tuning changes (main jet) similar to a non H.A.C.
carburetor. The only adjustments required on the Summit may be an idle speed reduction for
lower elevations.
Hose lengths from the carburetor to H.A.C. should not be altered. Shorter hoses will not affect the
calibration significantly, but care must be used to avoid kinking of the hoses. Too long of a hose
will cause a rich condition, because of reduced signal strength. While the H.A.C. units are identical
between the 583 and 467, on the '94 models, different hose routings are used because the 34 mm
carburetors have 90° fittings for the vent tubes, while the 38 mm carburetors exit straight out.
TROUBLESHOOTING
Lean Mixture
Rich Mixture
04-90
583 H.A.C. SUMMIT
490/490
480 Q-4
75
POSSIBLE CAUSE
1 ) Plugged hole in air jet inlet
2) H.A.C. frozen
2) Leakage in H.A.C. to carburetor tube
3) Leak in H.A.C. sealed chamber
4) H.A.C. frozen
583 STX
340/350
480 P-6
35