| Diagram | Fig. 25 — Basic Electrical Components — GROUP 25 · ref 30 |
| Listed in parts books | 1971–1973 |
Norton Resistor, Ballast
Ballast resistor for the ignition circuit, part number 47225A, appearing in catalog listings from 1971-1973.
This is the ballast resistor from the basic electrical components group, part number 47225A, showing up in catalog listings across 1971 to 1973. A ballast resistor works in series with the ignition coil to manage the voltage the coil sees once the engine is running, easing off some of the strain that would otherwise build up compared to a straight full-voltage feed.
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It's a small, easily overlooked component, but if it fails open the bike simply won't get a spark, and if it fails shorted the coil runs hotter than it should. Our catalog record doesn't tie this one to a specific model, so check what's on your bike now and confirm fitment before ordering.
If you're troubleshooting an ignition that cranks but won't fire, or a coil that's been running unusually hot, this is a component worth checking along with the usual points and coil suspects.
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