6.5 Carburettor heater hose (arrowed)
Remove the fuel tank (see Section 2). Place a suitable container beneath the carburettor drain hoses underneath the exhaust system, unscrew the carburettor drain screws and allow fuel to empty from the system (see illustration). Tighten the carburettor drain screws. Release the clips on the drain hoses and detach the hoses from the carburettors.
Release the clips on the crankcase breather hose between the valve cover and the air filter housing and remove the hose (see illustration).
Release the clip on the carburettor breather hose and detach the hose (see illustration 6.2),
Release the clip on the sub-air cleaner hose and remove the sub air cleaner assembly (see illustration 6.2)
Release the clips from the carburettor heater hoses and detach the hoses, being
Fuel and exhaust systems 4«5
6.10a
Inlet stub markings Carb UP (A), LH/RH (B) and carburettor clip
screws
at
top of stub (C)
6.7 Carefully lift the carburettors off the inlet stubs
6.10B Lug to locate inlet stub on head (a) and lug for clip on stub (b)
6.11A Fit carburettors into air filter housing
6.11b Throttle cables (A), crankcase
breather hose connection (B), carburettor
breather hose connection (C) and sub-air
cleaner hose connection (D)
prepared to catch any residual coolant (see illustration). Clamp or plug the hoses from the cylinder head union and the water pump to prevent undue coolant loss.
Detach the choke cable from the carburettors (see Section 11, Step 2).
Slacken the clamps on the cylinder head inlet stubs and the air filter housing, then ease the carburettors off the inlet stubs, lifting them upwards while at the same time tilting the air filter housing back (see illustration). The carburettors are a tight fit on the stubs and have to be completely free of them before they can be separated from the air filter housing. Note: Keep the carburettors as upright as possible to prevent the possibility of the piston diaphragms being damaged
Detach the throttle cables from the carburettors (see Section 10, Steps 3 and 4).
Release the clip securing the fuel supply hose to the inlet union on the carburettors and detach the hose.
Caution: Stuff clean rag into each cylinder head inlet after removing the carburettors to prevent anything from falling in.
10 If required, slacken the clamps securing the inlet stubs to the cylinder head and remove the stubs. The stubs are clearly marked; note which way round they fit and the location lugs on the underside of the head (see illustrations).
Installation
11 Installation is the reverse of removal, noting the following.
Check for cracks or splits in the cylinder head inlet stubs, and renew them if necessary.
If removed, make sure the inlet stubs are installed so that the slot in the underside
of the stub locates over the lug on the underside of the head (see illustration 6.10b).
Fit the carburettors into the air filter housing before fitting them into the inlet stubs (see illustration).
Make sure the carburettors are fully engaged with the inlet stubs and the clamps are securely tightened.
Make sure all cables and hoses are correctly routed and secured and not trapped or kinked (see illustration).
Refer to Section 10 for installation of the throttle cables and section 11 for the choke cable. Check the operation of the cables and adjust them as necessary (see Chapter 1).
Check idle speed and carburettor synchronisation and adjust as necessary (see Chapter 1).
I
7 Carburettors - disassembly, cleaning and inspection
A
Warning: Refer to the precautions given in Section 1 before starting work.
Disassembly
Remove the carburettors (see Section 6). Note: Do not separate the carburettors unless absolutely necessary; each carburettor can be dismantled sufficiently for all normal cleaning and adjustments while in place on the mounting brackets. Dismantle the carburettors separately to avoid interchanging parts.
Unscrew the heater hose union retaining screws and detach the unions, noting how
4*6 Fuel and exhaust systems
7.2 Heater hose union screw (arrowed)
7.3 Lift off the top cover and remove the spring
7.4 Diaphragm sealing groove (A) and tab recess (B)
they fit against the carburettor bodies (see
illustration).
3 Unscrew and remove the top cover
retaining screws. Lift off the cover and remove
7.5c Remove the spring (B) and discard the O-ring (A)
7.5b ... and pull the holder out of the piston
the spring from inside the vacuum piston (see
illustration).
4 Carefully peel the diaphragm away from its
sealing groove in the carburettor and
7.6 Remove the jet needle from the piston with the washer (arrowed)
withdraw the diaphragm and piston assembly.
Note how the tab on the diaphragm fits in the
recess in the carburettor body (see
illustration).
Caution: Do not use a sharp instrument to
displace the diaphragm as it is easily
damaged.
5 To remove the jet needle holder from the piston, thread a 4 mm screw into the top of the holder (one of the top cover retaining screws is ideal), then grasp the screw head with a pair of pliers and carefully draw the holder out of the piston. Note the spring that fits inside the holder. Discard the O-ring on the holder as a new one must be used (see illustrations).
Caution: Do not push the needle holder out of the piston by pushing up on the needle.
Push the jet needle up from the bottom of the piston and withdraw it from the top (see illustration). Note the washer that fits on the needle between the head of the needle and the piston.
Remove the screws securing the float chamber to the base of the carburettor and remove it. Remove the gasket and discard it as a new one must be used (see illustration).
Using a pair of thin-nose pliers, carefully withdraw the float pin (see illustration). If necessary, displace the pin using a small punch or a nail. Remove the float and unhook the float valve, noting how it fits onto the tab on the float (see illustration).
7.8a Withdraw the float pin (arrowed)
7.8b Shoulder (A) on float valve fits onto tab (B) on float. Note valve pin (C)
Fuel and exhaust systems 4*7
7.9 Main jet and jet holder (A), pilot jet (B) and pilot screw (C)
7.13a Remove choke linkage bar screws (arrowed)...
7.13b .. . and washers
9 Unscrew and remove the main jet from the base of the jet holder (see illustration).
Unscrew and remove the jet holder (see illustration 7.9).
Unscrew and remove the pilot jet (see illustration 7.9).
The pilot screw can be removed if required, but note that its setting will be disturbed (see Section 4). Unscrew and remove the pilot screw along with its spring, washer and O-ring (see illustration 7.9). Discard the O-ring as a new one must be used.
To remove a choke plunger, first remove the screws and washers securing the choke plunger linkage bar to the carburettors (see illustrations). Lift off the bar and remove the
collars and the return spring, noting how they fit (see illustrations).
14 Unscrew the choke plunger nut and withdraw the plunger and spring from the carburettor body, noting how they fit (see illustration). Take care not to lose the spring when removing the nut (see illustration).
Cleaning
Caution: Use only a petroleum based solvent for carburettor cleaning. Don't use caustic cleaners.
15 Submerge the metal components in the solvent for approximately thirty minutes (or longer, if the directions recommend it). After the carburettor has soaked long enough for the cleaner to loosen and dissolve most of the varnish and other deposits, use a nylon-
bristled brush to remove the stubborn deposits. Rinse it again, then dry it with compressed air.
16 Use a jet of compressed air to blow out all of the fuel and air passages in the main and upper body, not forgetting the air jets in the carburettor inlet.
Caution: Never clean the jets or passages with a piece of wire or a drill bit, as they will be enlarged, causing the fuel and air metering rates to be upset.