Engine - Poor Cold Operation
MAY 1984000 220
CJ/SCRAMBLER
3E
ENGINES - FUEL SYSTEMS Attention: Workshop and Parts Department
FOUR-CYLINDER ENGINE COLD OPERATION
Information
The choke on some 1984 four-cylinder YFA carburetors, may open too quickly after cold starts resulting in poor cold engine operation.
Service correction involves changing choke opening time as outlined in the following procedure.
Procedure
1. Remove the carburetor as outlined on page B-208 of the M.R. 252 manual.
FIGURE 1 - CARBURETOR BASE:
2. Disconnect the vacuum break supply hose from the vacuum supply tube in the carburetor base (Fig. 1).
3. Increase the diameter of the orifice in the vacuum supply tube with a 7/64-in. (0.109-in.) drill bit (Fig. 1).
NOTE: Be sure to remove all chips with compressed air after drilling out the orifice.
Figure 2 - Carburetor Delay Valve, Hoses and Vacuum Break:
4. Cut the vacuum break supply hose in two equal lengths and connect delay valve, 323 7293, to the two hose ends (Fig. 2).
NOTE: Install the valve with the brown side toward the vacuum break and the black side toward the supply tube.
5. Reset initial choke valve clearance to 0.275/0.280-in. (6.98/7.11 mm) as outfined on page B-225 of the M.R. 252 manual.
6. Reset fast idle cam index adjustment to 0.185-in. (4.62 mm) as outlined on page B-226 of the M.R. 252 manual.
Figure 3 - Choke Valve Closed:
7. Reset choke unloader adjustment to 0.300-in. (8.62 mm) as follows:
a. Hold the throttle lever (H) fully open and apply pressure on the choke, valve toward the closed position (Fig. 3).
Figure 4 - Choke Valve and Air Horn Wall Clearance Measurement:
b. Measure the clearance between the upper edge of the choke valve and the air horn wall (Fig. 4).
NOTE: It is not necessary to remove the air cleaner bracket when measuring the clearance between the choke valve and the air horn wall.. Position the gauge next to the bracket.
Figure 5 - Tang to Main Body Frame:
c. Adjust by bending the unloader tang (J), which contacts the fast idle cam (K) (Fig. 3). Bend toward cam (K) to increase clearance and away from cam (K) to decrease clearance (Fig. 5).
CAUTION: Do not bend unloader tang (J) downward from a horizontal plane. After making adjustment, be sure the unloader tang has at least 0.070-inch clearance (L) from the main body flange when the throttle is fully open (Fig. 5).
d. Operate the throttle and check unloader tang (J) to ensure it does not bind or contact any part of the carburetor casting or linkage.
8. Install the carburetor as outlined on page B-208 of the M.R. 252 manual. Then check for full throttle opening when throttle is operated by accelerator pedal.
9. Adjust fast idle speed, sole-vac vacuum actuator, and curb idle speed as outlined on pages B-229 through B-231 of the M.R. 252 manual.
Parts
Description Quantity Part Number
VALVE, DELAY 1 323 7293
GASKET, Carburetor Base 2 8953 000 617
S.R.T. Information
Operation
Operation Description T.I.C. Number S.R.T.
CO. CHOKE SYSTEM, YFA 1-222 1999 1.5
CARBURETOR - RECALIBRATE (Inc. idle speeds and choke unloader adjustment)
Filing Instructions
Record this I.S. on pages B-207 and B-229 through B-231 and file it in your M.R. 252 binder.