HS carburettor, tuning part 2
Check the piston damper oil level, to do this follow the next steps.
Step 1: Standard suction chambers. Unscrew the cap and withdraw the damper. Top up with oil (preferably S.A.E.20) until the level is just below the top of the hollow piston rod, refit the damper and screw the cap firmly into the suction chamber (6a).
Step 2: Ball bearing suction chambers (early type). Unscrew the cap and raise the piston and damper to the top of their travel. Fill the recess in the damper retainer with oil (preferably S.A.E. 20), lower the damper until the cap contacts the suction chamber, repeat this procedure until the oil level is just visible at the bottom of the retainer recess. Screw the cap firmly into the suction chamber. It is essential that the bearing retainer is not displaced from its position in the piston rod (6b).
Step 3: Ball bearing suction chambers (later type). Unscrew the damper cap and withdraw the damper. Top up with oil (preferably S.A.E. 20) to within 6.5 mm (0.25 in) of the top of the hollow piston rod. Refit the damper and screw in firmly.
Step 1: Vehicles with emission control. Connect a reliable tachometer to the engine in accordance with the instrument manufacturer's instructions.
Step 2: 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.
Step 3: Increase the engine speed to 2,500 r.p.m. for 30 seconds.
Step 4: Vehicles with emission control. Connect an exhaust gas analyser to the engine in accordance with the instrument manufacturer's instructions. Setting can now commence. If the correct setting cannot be obtained within three minutes, increase the engine speed to 2,500 r.p.m. for 30 seconds and then recommence tuning. Repeat this clearing operation at three-minute intervals until tuning is completed
Step 1: Adjust the throttle adjusting screw (1) until the correct idle speed is obtained (see vehicle manufacturer's tuning data).
Step 2:Turn the jet adjusting nut/screw (2) down/clockwise, to enrich or up/anti-clockwise to weaken, until the fastest speed is indicated; turn the nut/screw up/anti-clockwise until the engine speed just commences to fall. Turn the nut/screw down/ clockwise very slowly the minimum amount until the maximum speed is regained. From this setting adjust the mixture screw according to the vehicle manufacturer's recommendations.
Step 3: Check the idle speed, and readjust it as necessary with the throttle adjusting screw to obtain the correct setting.