1. Malfunctioning Throttle Cable: Check if there's tension in the throttle cable. If frayed or stretched, it could get stuck resulting in revving.
2. Carburetor Issues: Clean or inspect your carburetor as there could be dirt or a misadjustment there which may cause idle issues.
3. Leaking Vacuum Hoses: Inspect the vacuum hoses connected to the carburetor. Sometimes leaks in vacuum lines can also result in higher rpms.
4. Choke/Butterfly Valve: Inspect and clean the choke and its linkages that might affect fuel-air mix resulting in a high idle.
5. Idle Speed Adjustment: Your engine can sometimes simply be idling higher and will need re-adjustment.
Before making adjustments, make sure:
- Spark Plugs and wires are okay/good condition
- Ignition (distributor etc) is functioning well
- Carburetor air intake tube has a fresh clean fuel filter
