If you own a Motom and are looking for the right spark plug, you’ve come to the right place. This is one of the most talked-about topics among enthusiasts—and also one of the most misunderstood. The answer isn’t as simple as picking a spark plug from the catalog at your local shop—there are important factors to consider, first and foremost the condition of your coil and flywheel magnet.
The problem with modern spark plugs
Modern spark plugs have an internal resistance (also known as impedance) that helps reduce electromagnetic interference in modern vehicles. The problem is that this resistance interferes with vintage ignition coils, reducing their performance. The result: difficulty starting, lack of power, and a weak spark.
Golden rule: If you have a vintage ignition coil, use vintage spark plugs. If, on the other hand, you’ve replaced the coil with a modern one, you can consider using modern spark plugs—but always make sure the flywheel magnet is fully charged.
The Motom Candle Chart
The spark plugs listed in this table are taken directly from the original Motom manuals. The spark plug specifically recommended in the manual is highlighted in yellow. Conversions between old and new Marelli part numbers were made using the 1972 Magneti Marelli catalog.
How to read the table
- Candela Marelli old logo → the original logo from the Motom manual
- Candela Marelli's new theme song → the updated equivalent
- Lodge → equivalent in the Lodge catalog
- Electrode spacing → the gap in millimeters to be set
Conversions: Marelli → Lodge
For those looking for Lodge equivalents:
- Marelli CW175 = CN Lodge
- Marelli CW225 = HBN Lodge
- Marelli CW230 = HN Lodge
- Marelli CW240 = 2HN Lodge
- Marelli CW260 = 2HN Lodge
- Marelli CW275 = 3HN Lodge
A pink candle or a white one? It makes no difference!
If you have a vintage candle in your hand and notice that the ceramic is pink instead of white, don't panic—it's normal. Ceramics used to be made in pink; today they're white. The color has no effect on performance. What matters is the model number, not the appearance.
The spark plugs last for thousands of miles—the Motom is a 4-stroke!
There’s another common misconception: changing the spark plug as often as you would on a 2-stroke. The Motom is a 4-stroke, and the spark plugs last much longer. The proof? The TerreMotom trip—over 4,000 km covered without ever changing the spark plug. A Lodge 2HN installed at the start, still working perfectly at the end.
A practical tip: In the summer and on long trips, use a 2HN (a cooler spark plug that dissipates heat more effectively). In the winter, when the engine has a harder time warming up, a slightly hotter HN is better. It really makes a difference.
In summary
It’s always worth spending a little extra on the right vintage spark plug. The wrong spark plug can waste hours of your time troubleshooting a problem that doesn’t even exist. If you want to play it safe: follow the manual, use the codes in the table, and never underestimate the condition of the coil and the flywheel.
In the future, you'll also find an article on this site dedicated to coils and the flywheel magnet—with links to this guide.
Brochure images courtesy of Massimo Prata Motom Club Zurich
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