Guide: Converting a Floating Ground Stator to a Grounded Half-Wave System on a Honda CT70
This guide explains the differences between floating and grounded stators, how to convert a full-wave floating stator to a grounded half-wave system, and the implications for your electrical system.
Overview of Stator Types
Floating Ground Stator (Full-Wave System)
A floating ground stator is electrically isolated from the motorcycle frame. It has two output wires and neither is grounded. This allows both the positive and negative halves of the AC waveform to be used, making it ideal for full-wave rectification.
Benefits:
- Compatible with full-wave rectifiers
- Higher charging efficiency
- More consistent DC power
Modern motorcycles typically use full-wave floating stators with all-DC lighting systems. This allows for regulated, battery-backed power across all accessories, including LED lighting, fuel injection, and electronic displays.
Grounded Stator (Half-Wave System)
A grounded stator has one side of its coil tied directly to the motorcycle frame. This simplifies wiring and is compatible with half-wave rectification, which only uses one half of the AC waveform.
Commonly Used With:
- Half-wave rectifiers/regulators
- Simpler electrical systems (e.g., basic lighting and battery charging)
The Honda CT70 originally used a hybrid system. The headlight and taillight ran on unregulated AC directly from the stator, while the horn, battery charging, and turn signals ran on DC power supplied through a simple half-wave rectifier.
Converting from Floating to Grounded
Can You Ground a Floating Ground Stator? Yes. While we don't recommend it, grounding one side of the stator converts it into a grounded system. This involves connecting one of the stator output wires directly to the motorcycle frame.
How to Ground It:
- Identify one of the stator leads
- Use a clean, secure frame connection
- Ensure no other components expect the stator to be isolated
Result:
- You now have a grounded stator suitable for use with a half-wave regulator
Electrical Performance, Efficiency & Hybrid Use
If you're grounding a floating stator and using a half-wave regulator, you're creating a simplified electrical setup that works well for vintage applications.
Pros of This Setup:
- Simple and cost-effective
- Easy to wire
- Allows running AC lights directly off the stator without needing a battery
- Still provides some DC power for a horn, signals, or light charging
Cons:
- Only uses the positive half of the AC waveform
- Charging efficiency is reduced (usable power output drops by ~50%)
- DC output is pulsed and less stable
- Lighting may flicker or dim at low RPMs
- Undercharging risk, especially with modern accessories
- AC and DC loads share the same limited stator output
- Voltage instability if using mismatched regulators
- Heat buildup from running two regulators (AC and DC) in parallel
Efficiency Loss Explained:
Although the stator produces the same amount of energy, only half of the waveform is utilized in a grounded/half-wave system. This doesn't cut raw output in half, but it significantly reduces usable charging current.
Best Use Case:
- You have minimal electrical demand
- You want to run incandescent lights on AC
- You only need to trickle charge a small battery or power low-draw DC accessories
Summary & Recommendations
If you're simplifying your CT70's wiring and only need basic lighting and charging, grounding one side of your floating ground stator and using a half-wave regulator is a workable solution.
However, for best performance, especially with modern accessories, consider keeping the stator floating and using a full-wave rectifier/regulator to take full advantage of your stator's output.