Derbi

Engine Intake Info

• '86 and '87 SLE should be a flat reed engine (the flat reed engine came into play in '86)
  • You can tell if it has a steel rear swingarm on a Variant step through, it is a flat reed
  • If it has an alloy rear swingarm, it's piston port or pyramid reed
• the 81 SLE was pyramid reed
• Derbi RD's were pyramid reed
• Derbi Diablos and Lagunas piston port
• the Derbi DS50 scooter is flat reed

-quote by well known derbi connoisseur

Technical Specs

Piston port engines

• cylinder inducted
• stroke: 43mm
• bore: 38mm
• displacement: 48.7cc
• compression 8.5:1
• direction of rotation: counter clockwise facing magneto

Download the repair manual for Derbi piston port motors here.

Pyramid reed engines

• Pyramid 3-reed valve, Crankcase mounted
• stroke: 43mm
• bore: 38mm
• displacement: 48.6cc
• compression 8.5:1
• direction of rotation: counter clockwise facing magneto.

Flat reed engines

• Crankcase 2-reed valve induction with triple transfer port distribution
• stroke: 40mm
• bore: 39.87mm
• displacement: 49cc
• compression: 10:1
• direction of rotation: clockwise facing magneto.
• Max engine RPM: 6500
• Flywheel nut is reverse thread

See a PDF file of the flat reed engine repair manual here.

Make a Water-Cooled Derbi

Please see this discussion from the forums.

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