A3
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The Tomos A3 engine is a simple two stroke 49cc engine with a two speed automatic transmission. It is found on Tomos automatic models from the 70's until 1992. Depending on the model of A3 engine, they produce one to two horsepower with a maximum RPM of 4000-5500. This motor uses a Ducati 6v points type ignition. The A3 has a special flywheel alignment pin instead of the traditional woodruff key used by most other moped manufacturers. For more information on this pin, please see the woodruff key page.
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1991 and Previous Technical Specifications
- A3 Engine
- 49cc two stroke
- 38mm X 43mm Bore/Stroke
- 8.5:1 compression ratio
- Automatic 2 speed transmission
- Encarwi 12mm Carburetor (#50 jet) or Dellorto SHA 14/12 (#53 jet)
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Maintenance Information
- Gearbox oil: Type A or Type F Automatic transmission fluid.
- Spark plug: NGK B6HS, Bosch W4A2, Champion L82
- Spark plug gap: 0.5mm
- Timing advance: 1.8-2 mm BTDC
- Points Gap: 0.35-0.45 mm
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A3 Versions
The A3 came in three different versions -- the SL, GM, and SP (20, 25, and 30mph versions, respectively). For more technical data on the three models, read this.
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Related Articles
- Kit a Tomos A3
- Repair tutorial videos
- Changing Tomos transmission fluid
- Tomos A3 Carb Cleaning (Dellorto)
- Tomos A3 Carb Cleaning (Encarwi)
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Manuals
- 1988 workshop manual
- Spare parts manual
- Modified 1988 workshop manual (English-only and colored wiring diagrams)
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Repair Links
- An overview of the flywheel, points, transmission, and how to replace the transmission fluid
- A look at the gears and internal spring mechanism