1984-87 Prelude
Warning: This procedure requires a Honda special tool or equivalent.
1. Remove the air cleaner cover and filter.
2. Remove air intake screens and flanges.
3. Install sync adapters (tool 07504-SB00000 or equivalent) to each carburetor inlet; tighten the nuts only to 5 Nm.
4. Connect the tachometer and start the engine. Allow the engine to fully warm up until the cooling fans turn on at least once.
5. Use the carb timing tool to measure the flow ratio through both adapters. If the flows are the same - turn off the engine, remove the adapters and assemble the air cleaner. The test is over.
6. If the flows are different, loosen the adjusting screw locknut and adjust as needed. The adjusting screw only affects the right carburetor, so use the value of the left carburetor as a baseline. Turn the adjusting screw clockwise to decrease the airflow; counterclockwise to increase flow. If the air flow cannot be balanced, check the carburetor or carbon nozzle on the throttle for air leaks.
7. Tighten the adjusting screw locknut. Recheck the flow ratio.
8. Stop the engine. Remove the synchronizer and adapters. Install flanges and air intake screens.
9. Reassemble the air filter and cover.
1988-90 Prelude
1. Disconnect the red braided hose (marked PURGE) from the tank. Connect the vacuum gauge to the hose.
2. Connect the tachometer and start the engine. Let the engine run until it reaches normal operating temperature; the cooling fan should turn on at least once.
3. Turn the idle speed adjusting screw until the engine speed is 3000 rpm. Pay attention to the value on the manometer.
4. With the engine running at 3000 rpm, pinch the smooth red vacuum hose under the throttle body and note the change, if any, on the gauge.
5. If there was no change on the gauge, the carburettors are correctly timed.
6. If there was a change when the hose was pinched, adjust the timing screw until the values no longer change.
7. Remove the vacuum gauge and connect the PURGE hose to the canister. Remove the tachometer.
8. Reset idle speed.