MG MGB TOURER GHN5 Handbook page 74

Fuel System
4. Ensure that the mixture control (choke) will return fully, that the cable has
&
in. free play (1) before it starts to pull on the lever and a small clearance (2)
exists between the fast idle screws and their cams when the cams are against
their stops (3).
5. Raise each carburetter piston with the lifting pin
(4),
release the pin and
check that the piston falls freely onto the bridge of the carburetter, indicated
by a distinct metallic click. If the piston fails to fall freely, consult your
Distributor or Dealer.
6. Connect a reliable tachometer.
7. Start the engine and run it at a fast idle speed until it attains normal running
temperature then run it for a further five minutes.
8. Increase the engine speed to 2,500 r.p.m. for thirty seconds.
NOTE.-Tuning can now be commenced. If delay prevents the adjustment being
completed within three minutes, increase the engine speed to 2,500 r.p.m. for
thirty seconds and then continue tuning. Repeat this clearing procedure at three-
minute intervals until tuning is completed.
9. Check the idle speed (tachometer) see 'GENERAL DATA' and check the
carburetters for balanced air intake using a balance meter.
10. If the balance is not correct, adjust as follows: release a throttle connector
(9) between the carburetters and turn the adjusting screw (5) on one of the
carburetters until the balance is correct. Then adjust the idle speed by
turning the throttle adjusting screw (5) on each carburetter by the same
amount. Re-check the carburetter balance.
Check the throttle shaft pin clearance and adjust if necessary-see para-
graph (18).