Revised 11-19-2013
Introduction
All Honda CX/GL motorcycles have a liquid cooling system. When the bike is in motion at normal riding speeds, there is plenty of airflow through the radiator to prevent engine overheating.
But when the bike is stopped or slowly moving, airflow through the radiator can be insufficient. To handle this situation, a fan mounted behind the radiator is used to pull air though the radiator. The non-turbo 500 bikes use a mechanical fan mounted directly to the camshaft. The turbo-500 and all 650 bikes use an electric fan.
Both fan implementations were satisfactory back in the day, but with passing years several common problems have become evident. This write-up addresses those problems.
Corrective actions taken for my own bikes are described in detail. My bikes are all GL's, but the recommended upgrades are also applicable to CX's. If you are considering similar cooling system upgrades, hopefully the information presented may give you some ideas and help answer questions that may arise.
For the mechanical fan bikes, henceforth referred to simply as 500's for brevity, conversion to an electric fan is highly recommended, including usage of a fan power relay. A compelling justification for the electric fan conversion is presented.
Factory electrical fan bikes, similarly referred to as 650's for brevity, also have room for improvement. My recommendations include installation of a fan power relay and replacing the radiator temperature switch with one that operates at a lower temperature.
Acknowledgement
Special thanks and recognition are due to CX/GL Forum member Shep. In addition to his longstanding technical contributions to the forum, he was an early adopter and continues to be an advocate of electric fan conversions for the 500's. A significant portion of the information presented in this write-up owes its existence to his background research and advice. Shep also started and maintains the CX500 GL500 650 Global Forum.
Wiring Tips and Suggestions
Prior to proceeding with any wiring modifications, a few minutes should be spent reviewing this brief Wiring Fabrication and Repairs write-up. It contains several tips and identifies sources for hard-to-find parts that may make the task easier.
Detailed Information
The following sections can be viewed sequentially or you can jump directly to the ones applicable to your bike. Each link is annotated to indicate applicability.
Electric Fan Conversion Justification 500
only
Tachometer Cable Screw Replacement 500 and 650
Electric Fan Selection and Mounting 500 only
Camshaft Clearance Considerations 500 only
Fan Power Relay 500 and 650
500 Radiator Temperature Switch 500 only
650 Radiator Temperature Switch 650 only
Fan Always-On Modification 500 and 650