Tomos A55 Technical and Tuning





  • 49cc two stroke
  • 38mm X 43mm Bore/Stroke
  • 10:1 compression ratio
  • Automatic 2 speed transmission
  • Piston port intake
  • Dellorto PHVA 14mm Carburetor (#55 main jet, #25 pilot, #40 choke)
  • Gearbox oil: Type A or Type Automatic Transmission Fluid
  • Spark plug: NGK BR8ES, Gap = .85mm
  • Front Sprocket: 26T
  • Rear Sprocket:  31T
  • Chain Size 415 x 104 links
    The A55 engine was so well designed that restrictions were put into place to pass emissions and safety standards.
  • Replace the larger 27T rear sprocket with a  22T or 24T.  The  22T will give you the best top speeds but you will lose low end.  Not good for areas with big hills and heavier riders.  24T is the best all around size for higher top speed, but retains good low end power. 
  • A55 Speed Kit-  High flow air filter and jetting. Increase top end and midrange.  Best used with a performance exhaust.  
  • Performance exhaust.  Stock exhausts are not designed for performance, are very heavy and restricts flow.  The key to unlocking the power of a 2 stroke is in the expansion chamber.
HERE is a great write up from the Netherlands.  Provides good knowledge of the A55 engine based mopeds along with general engine basics and tuning tips.  Written by Marctraider

The title says it all....  Mostly for the advanced tuners.






UNDER CONSTRUCTION:  More info will be added soon.  Please check back!