Reason for the wiring modification:
With many aspects of vintage Honda motorcycles it is common to find a bit of "over engineering" aka making things more complex than they need to be and sometimes a bit of "under engineering" on specific parts. The charging system on the Honda CB175 / CB350 (twin) / CB360 & CB450 family of bikes is a victim of both situations at the same time. The charging system in all of these bikes is a permanent magnet single phase design, however even in top form the particular design of these systems is on the anemic end of the spectrum thus "under engineered." To complicate matters more Honda took the stator coil assembly and divided it into two sections. One half of the system is "ON" all the time, producing charging current when the engine is running (this is the yellow wire). The other half of the system was switched "ON" when the rider also switched on the headlight (this is the white wire w/ yellow stripe). This is a logical jump as the headlight draws a good bit of additional power, and therefore switching on the second half of the stator coil to increase charging current makes sense. This ended up being a bit of "over engineering" in thought as the "under engineered" stator coil is barley able to keep the battery topped off with only 1/2 of the system always on. Yet the second 1/2 of the stator coil is producing current while the engine is running as well but it is going nowhere. This additional charging current is wasted because its routing back to the rectifier is integrated to the headlight on / off switch. If the headlight is off, then the additional charging current is wasted.
What the white / yellow wire modification does is bypass the routing of the second half of the stator coil through the head light ON / OFF switch, therefore allowing both halves of the stator coil to always be "ON" regardless if the headlight is on or not. This means the maximum output potential of the stator coil when the engine is running on the bike, which it does need.
This mod does not affect the actual headlight switch controlling the ON / OFF function of the headlight bulb.
Although this modification improves the performance of the charging system, the overall low output of the system design does mean a you need to keep a few things to keep in mind:
- Typical charging voltages are about 12.5 to 13.2 VDC from the system, anything over 12VDC is acceptable.
- All of these bikes need a top notch healthy battery to run properly, we recommend an AGM style battery and that you keep the battery on a maintainer / charger when storing the bike.
- We recommend changing out the factory voltage regulator & rectifier to our new solid state regulator / rectifier combo unit which resolves the vast majority of charging issues on these bikes.
- The charging system does not have enough output to charge a low, weak or discharged battery. This can work in a car with a large alternator, but the system in these bikes can not handle that kind of load. Charge the battery on the proper charger for the type of battery and check the voltage before starting the bike or replace the battery with a known good one.
- Headlights draw an incredible amount of power, keep bulb wattage under 35W. We have several options for headlight upgrades that keep the watts in spec while increasing the light output of the system for a brighter headlight. Headlight lens & bucket options
How to make the mod:
To make the white/ yellow wire mod first unplug the yellow and white wire w/yellow stripe wires from the connectors that route the current into the right hand switch box (where the headlight ON / OFF switch is). The disconnected wires from the switch box can be left alone as they will now be "dead." On the main wiring harness plug the male end of the yellow wire into the female end of the white wire w/ yellow stripe which is also on the main harness. The female end of the white w/ yellow stripe wire you are looking for has a half clear and half yellow sleeve over the connector. Depending on the harness design there may be a small jumper wire about 2 inches long on one of the two wires mentioned above. Typically you will not use this jumper and it can be removed.
Below is a photo of what the connection looks like and how the two ends look once properly joined. This modification requires no tools and only takes a few moments of time finding the right wires and connecting them up. Watch our video of us doing the modification on each bike to better familiarize yourself with how perform this modification.
Honda CB175 / CL175 / CB200 / CL200 Owners:
- You will find these connections inside the headlight bucket.
Honda CB350 / CL350 / CB450 / CL450 Owners:
- You will find these connections inside the headlight bucket.
Honda CB360 / CL360 Owners:
- You will find these connections underneath the fuel tank.
Also check out our article on how and why to change your stock regulator and rectifier over to a modern combination regulator/rectifier unit. This is the other most important modification to do to your charging system. Click here to go there.