Vacuum Controlled Secondary
- Disconnect secondary diaphragm vacuum hose and connect a vacuum pump to diaphragm. See Fig 1
. Open throttle valve fully and apply vacuum. Ensure diaphragm rod moves as vacuum is applied and that vacuum remains steady. If vacuum does not hold or rod does not move, check for proper hose connection and condition. If okay, replace diaphragm and retest.
- With engine cold, coolant temperature less than 122°F (50°C), disconnect vacuum hose from vacuum "T" fitting. Connect a vacuum pump to "T" fitting and apply vacuum. See Fig 1
. Vacuum should not hold. If vacuum holds, ensure hose is not clogged. If hose is okay, replace thermovalve "D".
- Warm engine to normal operating temperature. Disconnect vacuum hose from vacuum "T" fitting. Connect a vacuum pump and apply vacuum. See Fig 1
. Vacuum should remain steady. If vacuum does not remain steady, check hose for proper connection and condition. If hose is okay, replace thermovalve "D".
- Disconnect vacuum hose from "T" fitting and connect vacuum pump. Apply vacuum. Vacuum should not hold. If vacuum does not hold, test is complete. Reconnect all connections. If vacuum holds, check "T" fitting, hose and clean carburetor port. Clean or replace as necessary.
Courtesy of AMERICAN HONDA MOTOR CO., INC.