CHT Sensor Guide
AiM CHT (Cylinder Head Temperature) Sensor Guide
This guide explains how the AiM CHT sensor works, what temperatures you should expect, and how to diagnose issues using MyChron 5 and MyChron 6 data. This information is tailored for kart racers in New Zealand and Australia.
What the CHT sensor measures
The CHT sensor measures the temperature of the cylinder head by using a special washer that sits under the spark plug. It is essential for monitoring:
- Air‑cooled engines (Briggs, Yamaha, Vortex Mini Rok)
- Engine safety and reliability
- Jetting and tuning accuracy
- Overheating or detonation risk
Why CHT matters
Air‑cooled engines rely heavily on airflow and mixture for cooling. CHT gives a direct indication of how hot the engine is running, helping you:
- Prevent overheating
- Tune jetting correctly
- Diagnose airflow issues
- Monitor engine health over time
Ideal CHT temperature ranges
| Engine | Ideal CHT |
|---|---|
| Briggs & Stratton | 150–180°C |
| Yamaha KT100 | 180–200°C |
| Vortex Mini Rok | 160–180°C |
How to read CHT data
In AiM RaceStudio 3, CHT appears as a smooth rising curve. Look for:
- Warm‑up phase: steady rise to operating temperature
- Stable phase: temperature holds within ideal range
- Spike phase: sudden rise indicates airflow or jetting issues
Common CHT problems and symptoms
| Symptom | Likely Cause | Fix |
|---|---|---|
| CHT too high | Lean jetting, blocked airflow, hot weather | Increase jet size, improve airflow |
| CHT too low | Rich jetting, cold weather | Reduce jet size |
| Erratic readings | Loose spark plug or sensor washer | Tighten plug and check washer |
| Sudden spikes | Detonation or airflow blockage | Check jetting and cooling shrouds |
How to tune using CHT
CHT is one of the best tuning indicators for air‑cooled engines:
- High CHT: engine running lean → increase jet size
- Low CHT: engine running rich → decrease jet size
For Yamaha, Briggs, and Vortex Mini Rok engines used in NZ & AU, CHT is more reliable than EGT for tuning.
Maintenance tips
- Ensure spark plug is tightened correctly
- Inspect the CHT washer for damage
- Keep wiring away from ignition interference
- Check airflow shrouds and cooling ducts