The Simson S51 is an East German classic chain-drive 50cc two-stroke — a geared mokick / light motorcycle in period terms, not a modern CVT scooter. US examples are uncommon; EU parts patience is part of ownership. This page leads with company history and the S50→S51 lineage, then high-level ownership notes. Full service procedures belong in the manuals.

Company history — Suhl to the S51

Secondary histories place Simson in Suhl, with roots commonly dated to the mid-1850s as a metalworking / arms-related enterprise. During the Nazi period the firm was seized — noted here only as a brief factual waypoint. After 1945 the works continued in the GDR under state industry (commonly described as a VEB Simson operation in Suhl).

By the early 1960s, secondary accounts say Simson’s four-stroke motorcycle lines wound down (around 1962) and road production shifted into small two-strokes: mopeds and mokicks. The sheetmetal Schwalbe (KR) is a short ancestor in that story — popular, but not the subject of this page.

The mid-1970s S50 brought a more modern angular look while keeping chain drive and a foot-shifted gearbox. The S51 follows in that line. Medium confidence: S51 production is commonly placed in the ~1980s (into reunification-era leftovers on the used market). Exact start/stop months stay secondary until a factory sheet is cited. Do not invent S51 electrics or trim packages from S50 nickname lists — read the stamps on the bike in front of you.

What an S51 is (and isn’t)

On MopedMasters the S51 is a classic chain-drive moped / lightweight with a sequential gearbox — not a belt scooter, and not a Puch-style single-speed centrifugal-only story. Trim letters and switchgear varied; this page does not publish a trim matrix.

Engine & drive (starting-point — verify in manual)

Commonly documented powertrain notes for this family (all medium confidence — verify in your manual; not yet confirmed from a factory source, and not carried over from S50-only material):

  • Long-stroke single often listed around 38 × 44 mm bore/stroke (~49.8 cc).
  • Engine codes often cited as M531 / M541 (3-speed vs 4-speed contexts in secondary sources — confirm on your cases).
  • Ziehkeil (draw-key) gearbox with 3- or 4-speed variants — foot shift.
  • Chain final drive.
  • Premix commonly quoted around 1:50 — verify in your manual for your engine code and condition. No PS / hp claims here.

Do not copy Bing or Dellorto jet tables from Puch/Tomos pages onto a Simson. No stock jets, timing degrees, or torque figures until they are confirmed from a factory source.

US ownership & parts scarcity

  • Expect EU suppliers and shipping delays; budget cables, covers, and small hardware.
  • “S51” marketplace titles sometimes hide S50 or mixed engines — read the stamp.
  • Learn the shift and clutch before blaming jets; a missed Ziehkeil shift is not a mixture problem.
  • Diagnose electrics with a diagram for your variant.
  • Legal class: US moped laws (not legal advice — verify with your DMV; laws change).

Performance posture

Stock-sorted and healthy before pipes. No mph guarantees, no invented jets, no shop names. Intake/exhaust changes mean plug-chop via carb jetting with Simson starting jets left to your manual. Lean mixtures seize top ends.

Buying checklist

  • Warm compression vs a known-good runner; turns freely through the gears.
  • Frame rust; swingarm and chain wear.
  • Shift all gears off-load; note clutch slip or false neutrals.
  • Title / VIN match; budget carb clean, plug, fuel lines, chain service.
  • Full process: buying guide.

FAQ

Is the Simson S51 a moped or a scooter?
Classic chain-drive moped / lightweight with a foot-shifted gearbox — not a modern CVT scooter. See moped vs scooter.
S50 vs S51?
Secondary histories place the S50 in the mid/late 1970s and the S51 in the ~1980s. Confirm with stamped codes; do not invent S51 parts from S50 trim lists.
What oil mix should I use?
Common starting point ~1:50 premix — verify in your manual.
Where should I start after buying one?
Identify the engine stamp, fresh fuel/plug/lines, correct premix, chain care, careful first ride through the gears. Then maintenance and manuals.

Manuals & PDFs →