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really big verson

GENERAL

• Refer to section 3 for carburetor synchronization, throttle cable and choke cable adjustments.
• When disassembling fuel system parts, note the locations of the O-rings; Replace them with new ones on reassembly.
• The carburetor float chambers have drain screws that can be loosened to drain residual gasoline.
• For fuel pump inspection refer to section 18.
• All hoses used in the evaporative emission control system are numbered for identification.  When connection one of these hoses, copare the hose number withthe Vacuum Hose Routing Diagram Lable on Page 4-15 (California model only), for its routing

TOOLS

Special

Common

Engine cranks but won’t start

• No fuel to carburetor
• Engine flooded with fuel
• No spark at plug (ignition system faulty)
• clogged air cleaner
• Intake air leak
• Improper choke operation
• Improper throttle operation

Hard starting or stalling after starting

• Improper choke operation
• Ignition malfunction
• Faulty carburetor
• Fuel contaminated
• Intake air leak
• Incorrect idle speed
• Incorrect valve clearance (section 3)
• Incorrect carburetor syncronization (section 3)
• Improper choke valve operation

Rough idle

• Faulty ignition system
• Incorrect idle speed
• Incorrect valve clearance (section 3)
• Incorrect carburetor syncronization (section 3)
• Faulty carburetor
• Fuel contaminated
• Faulty air cut-off valve (California model only)
  • Faulty purge control valve
  • Faulty air vent control valve
  • worn/damaged emission system hoses

Afterburning during deceleration

• Faulty ignition system
• Faulty air cut-off valve (California model only)
• Lean mixture
  (California model only:)
  • worn/damaged emission system hoses

Misfiring during acceleration

• Faulty ignition system

Backfiring

• Faulty ignition system
• Faulty carburetor

Poor performance (drivability) and poor fuel economy

• Clogged fuel system
• Faulty ignition system
• Dirty air cleaner
• (California model only:)
  • Faulty air vent control valve
  • Worn/damaged emission system hoses

Lean mixture

• Clogged fuel jets
• Stuck vacuum piston
• Faulty float valve
• Low float level
• Clogged fuel tank breather
• Clogged fuel strainer
• Restricted fuel line
• Intake air leak
• Restricted or faulty fuel pump

Rich mixture

• Clogged air jets
• Faulty float valve
• Float level too high
• Dirty air cleaner

Remove the seat (page 13-25) and turn the fuel valve OFF.
Disconnect the fuel tube from the fuel tank.

All models:
Remove the rear fuel tank mounting bolt first, then the front bolt and remove the tank from the frame.

Check that fuel flows out of the fuel valve freely.
If flow is restricted, clean the fuel strainer.

All models:
Remove the fuel tank from the frame.

’88, After ’88:
Install the fuel tank in the frame.
Install the front mounting collar and the bolt first, then the rear mounting bolt.

Connect the removed tubes securely.

Remove the seat and fuel tank.
Remove the air cleaner case mounting bolt.

Loosen the air cleaner connecting tube band screws and disconnect the crankcase breather and air cleaner case drain tube.
Remove the air cleaner case.

Install the air cleaner case in the reverse order of removal.

Remove the following:

• seat (page 13-25) and fuel tank (page 4-3)
• air cleaner case

Wash the element in non-flammable or high flash point solvent, squeeze out the solvent thoroughly, and allow the element to dry.
Soak the element in gear oil (SAE #80 - 90) and squeeze out the excess.
Reinstall the element and cover, and tighten the bolt.
Reconnect the air tubes from the carburetors.

Loosen the drain screws and drain the fuel into a container.
Remove the air cleaner case.
Disconnect the throttle cables from the carburetor.

Remove the choke valves from the carburetor and loosen the carburetor insulator bands.

California model only:
Disconnect the purge control valve No. 5 tubes and air vent control valve No. 6 and 11 tubes from the carburetor.

Pull the carburetors upward and away from the engine.

Remove the fuel tube from the carburetor.

Remove the four screws and vacuum chamber cover.

Remove the spring, piston/diaphragm.
Inspect the vacuum piston for wear, nicks, scratches or other damage.

Make sure the piston moves up and down freely in the chamber.

Push the jet needle holder in and turn it in 90 degrees counterclockwise.

Then remove the needle holder, spring, jet needle and from the piston.
Inspect the needle for excessive wear at the tip, bending or other damge.
Inspect the diaphragm for damage, fatigue or pin holes.
Inspect the vacuum piston for wear or damage.

Remove the four screws and float chamber.

Remove the float pin, float and float valves.

Remove the main jet, needle jet, slow jet and valve seat/filter.

Check each part for wear or damage.
Blow open all jets with compressed air.

Clean each jet with non-flammable or high flash point solvent.

Inspect the float valve seat and filter for grooves, nicks or deposits.

Clean the filter with low-pressure compressed air.

HINT: You don’t need a special screw to remove the cap.  Any small sheet metal or wood screw will work as long as its width is enough to grab the hole and it isn’t so pointy as to hit the pilot screw.  File the tip down to be extra careful.

Turn each pilot screw in and carefully count the number of turns until it seats lightly.  Make a note of this to use as a reference when reinstalling the pilot screws.

Remove the pilot screws and inspect them.  Replace them if they are worn or damaged.

Remove the two screws, the set plate and the air cut off valve cover.

• diaphragm for deterioration, pin hole or other damage.
• spring for deterioration or other damage.
• diaphragm needle for excessive wear at the tip or other damage.
• orifice of air vent for clogging.
• O-ring for damage.

Separate the carburetors (page 4-12).
Remove the float valve, all jets, and the pilot screws.
Blow open all carburetor body openings with compressed air.

If the air tube joint was removed, install a new O-ring onto the air tube joint.

Install the air cut off valve cover with the joint set plate and tighten the screws securely.

Be sure the diaphragm and spring are properly seated.

Install the pilot screws and return them to their original position as noted during removal.

Perform pilot screw adjustment if new pilot screws are installed (Page 4-14).

Install the pilot screw and turn it in until it seats lightly.
Turn the pilot screw out the number of turns recorded during removal.

Install the valve seat, slow jet, needle jet and main jet.

Install the float with float valve in the carburetor body, then install the float arm pin through the body and the float.

Measure the float level with the float tang just contacting the float valve.

FLOAT LEVEL: 9.2 mm (0.36 in)

Adjust the float level by carefully bending the tang.

Install the new O-ring in the float chamber groove.

Install the washer, jet needle, spring and jet needle holder in the vacuum piston.

Push the jet needle holder in and turn it in 90 degrees clockwise.

Hold the vacuum piston up to almost full open to avoid pinching the diaphragm with the chamber cover.

Install the vacuum piston, aligning the tab of the diaphragm with the groove of the carburetor.

Install the chamber cover with the spring, aligning the cover with the hole in the carburetor, and secure with at least two screws before releasing the vacuum piston.

Install the fuel tubes as shown.

Loosen the synchronization adjusting screw.

Loosen the synchronization adjusting screw until there is no spring tension.

Install the thrust spring between the throttle links.

Secure the carburetors together with the two screws.

Install the synchronization spring and synchronization adjusting screw.

Inspect throttle operation as described below:

• Open the throttle slightly by rotating the throttle valve, then release the throttle.  Make sure that there is no drag when opening and closing the throttle.

Turn the throttle stop screw to align the rear cylinder carburetor
throttle valve with the edge of the bypass hole.

Align the front cylinder carburetor throttle valve with the bypass hole edge by turning the synchronization adjusting screw.

Make sure the throttle returns smoothly to the fully closed position.

Install the carburetors onto the cylinder heads and tighten the insulator bands securely.

• air cleaner case
• fuel tank
• throttle cables
• choke cables

• pilot screw
• carburetor synchronization (page 3-8)
• throttle grip free play (page 3-4)
• carburetor idle speed (page 3-9)
• carburetor choke (page 3-5)

1. Turn each pilot screw clockwise until it seats lightly and back it out to the specification given.
   This is an initial setting prior to the final pilot screw adjustment.

INITIAL OPENING:

2. Warm up the engine to operating temperature.
   Stop and go riding for 10 minutes is sufficient.
3. Attach a tachometer according to the manufacturer’s instructions.
4. Adjust the idle speed with the throttle stop screw.
5. Turn each pilot screw 1/2 turn out from the initial setting.
6. If the engine speed increases by 50 rpm or more, turn each pilot screw out by an additional 1/2 turn until engine speed drops by 50 rpm or less.
7. Adjust the idle speed with the throttle stop screw.
8. Turn the rear cylinder carburetor pilot screw in until the engine speed drops 50 rpm.
9. Turn the rear cylinder carburetor pilot screw 1 turn out from the position obtained in step 8.
10. Adjust the idle speed with the throttle stop screw.
11. Perform steps 8, 9 and 10 for the front cylinder carburetor pilot screw.
12. Drive new pilot screw plugs into the pilot screw bores with a 7 mm valve guide driver (P/N 07942—8230000).  When fully seated the plug surfaces will be recessed 1 mm.

When the vehicle is to be operated continuously above 2,000m (6,500 feet) the carburetors must be readjusted as follows to improve driveability and decrease exhaust emissions.
Remove each pilot screw plug (page 4-7).
Warm up the engine to operating temperature.  Stop and go riding for 10 minutes is sufficient.
Turn each pilot screw clockwise 1/2 turn.
Adjust the idle speed to specification with the throttle stop screw.

IDLE SPEED: 1,200 + 100 rpm

Drive new pilot screw plugs into the pilot screw bores (page 4-7).
Attach a Vehicle Emission Control Information Update label on the left sub-frame upper pipe as shown.  See SL#132 for information on obtaining the label.

When the vehicle is to be operated continuously below 1,500m (5,000 feet), turn each pilot screw counterclockwise 1/2 turn to its original position after removing each pilot screw plug and adjust the idle speed to specification (page 4-1).  Drive new pilot screw plugs into the pilot screw bores (page 4-7).  Be sure to do these adjustments at low altitude with the engine at normal operating temperature.

Check all fuel tank, Purge Control Valve (PCV), and charcoal canister hoses to be sure they are not kinked and are securely connected.  Replace any hose that shows signs of damage or deterioration.

Disconnect the PCV hoses from their connections and remove the PCV from its mount.  Refer to the routing label on the air cleaner case cover for hose connections.

Connect a vacuum pump to the 8 mm (0.31 in.) I.D. hose No. 5 that goes to the 3-way joint.  Apply the specified vacuum to the PCV.

SPECIFIED VACUUM: 250 mm (9.8 in) Hg

Remove the vacuum pump and connect it to the vacuum hose No. 11 that goes to the left carburetor body.
Apply the specified vacuum to the PCV.

The specified vacuum should be maintained.
Replace the PCV if vacuum is not maintained

Connect a pressure pump to the 8 mm (0.31 in.) I.D. hose No. 4 that goes to the charcoal canister.  While applying the specified vacuum to the PCV hose that goes to the 3-way joint pump air through the canister hose.  Air should flow through the PCV and out of the hose that goes to the 3-way joint.
Replace the PCV if air does not flow out.

Remove the pumps, install the PCV on its mount, route and reconnect the hoses according to the routing label (page 4-18).

Disconnect the Air Vent Control Valve (AVCV) hoses from their connections and remove the AVCV from its mount.  Refer to the routing label on the air cleaner case cover for hose connections.
Connect a vacuum pump to the No. 10 hose that goes to the right carburetor body.
Apply the specified vacuum to the AVCV.

SPECIFIED VACUUM: 250 mm (9.8 in) Hg

The specified vacuum should be maintained.  Replace the AVCV if vacuum is not maintained.

Connect the vacuum pump to the air vent port of the AVCV.  Apply vacuum to the AVCV.  The vacuum should hold steady.  Replace the AVCV if vacuum leaks.

Connect the vacuum pump to the No. 10 hose that goes to the right carburetor body.
Connect the pressure pump to the air vent port of the AVCV.  While applying the vacuum to the AVCV No. 10 hose that goes to the right carburetor body, pump air through the air vent port.
Air should flow through the AVCV and out of the hose that goes to the carburetor air joint pipe.

Plug the hose that goes to the carburetor air joint pipe.
While applying vacuum to the AVCV No. 10 hose that goes to the 3-way joint, apply air pressure.  It should hold steady.

Replace the AVCV if pressure is not retained.
Remove the pumps, install the AVCV on its mount, route and reconnect the hoses according to the routing label.

SYSTEM INSPECTION

Check that the secondary air intake ports are clean and free of carbon deposits.

Check the secondary air intake hose for clogging, deterioration or damage and replace if necessary.
Check the reed valves in the air suction valve (ASV) if the intake hose or supply hose is damaged by exhaust gas.
Disconnect the vacuum tube (No. 10) from the ASV and install a plug in the vacuum tube to keep air from entering.
Connect the vacuum pump to the ASV.

Start the engine and open the throttle slightly to be certain that air is sucked in through the intake hose.
If air is not drawn in, check the air supply hoses and vacuum tube for clogging.
With the engine running, gradually apply vacuum to the ASV.  Check that the air intake hose stops drawing air, and that the vacuum does not bleed off.

SPECIFIED VACUUM:
   300 - 370 mm (1 1.8 - 14.6 in) Hg

If air is still drawn in, or if the specified vacuum is not maintained, install a new ASV.
If afterburn occurs on deceleration, even when the secondary air supply system is normal, check the air cut-off valve for correct vacuum operation.

Disconnect the air supply hoses from the reed valve covers of the ASV.
Disconnect the vacuum tube and air intake hose from the ASV.
Remove the ASV mounting bolts and ASV.

Remove the two screws, the reed valve cover and the reed valve from the ASV.

Check the reed valve for damage or fatigue, and replace if necessary.

Install a new reed valve if the seat rubber is cracked or damaged, or if there is clearance between the reed valve and seat.

Assemble and install the ASV in the reverse order of disassembly/removal.