1978 Ski-Doo Shop Manual, Page 236Get this manual
SECTION 04 SUB-SECTION 05, (CARBURETOR)
Air bubbles escaping from inside the carburetor bore indicates leaking inlet needleBubbles escaping from leaking gasket or diaphragm indicates tightening or replacement
Low speed mixture
With engine off, gently turn idle mixture screw fully clockwise until closed, then back off 'l ts turns114-0 counter-clockwiseCAUTION: When pulling heavy loads such as trail groomer, it is strongly recommended to enrich the Low Speed Mixture by turning the screw 14 of turn counter-clockwise
INSTALLATION
To install carburetor on engine, inverse removal procedureFor identification purposes, the fuel return line inlet on the tank male connector is stamped with the letters "IN"
Idle speed
Allow engine to warm then using screwdriver, turn the idle speed adjusting screw clockwise to increase idling speed, counter-clockwise to decreaseAdjust to 15001800 RPM
High speed mixture
A primary adjustment, with engine off, should be made by first turning high speed mixture screw fully clockwise until closed, then back off 14 turns14 counterclockwiseFor final adjustment, start engine and allow it to warmDrive the vehicle for approximately 1.6 km (1 mile) at 6,000 RPM(The high speed jet will be operational at this RPM range)Stop the engine immediatelyRemove spark plug and inspect plug faceThe plug face will indicate whether the mixture is rich, normal or leanA brownish tip reflects ideal carburetor adjustmentA black insulator tip indicates rich mixtureLight grey insulator tip indicates lean mixtureIf the mixture is incorrect, readjust 18 of turn and recheck color of spark plug face