Maintenance

Two-stroke oil mix

Most vintage mopeds use premix (fuel + oil in the tank). Ratios vary by manufacturer — see our two-stroke oil guide. Honda NC50/PA50II are still two-strokes but use a separate oil injection tank instead of premix — see the Honda guide.

Spark plugs

Check gap and condition every season. Common sizes: NGK B6HS (Puch), B7HS (Tomos/Honda). Replace if fouled or worn — cheap insurance against hard starting.

Chain-drive bikes (Puch, Tomos, Peugeot)

Chain: Check tension and lubricate. Puch: ~12 mm (½″) free play at midpoint. Tomos A55: ~10 mm free play. Peugeot: follow variator cover specs.

Transmission: Tomos A35/A55 use automatic two-speed gearboxes — not belts. Change Type A or F ATF in the transmission case on schedule (see Tomos guide).

Clutch: Puch E50 — one-speed centrifugal clutch in the clutch bell. Puch ZA50 and Tomos — automatic two-speed with internal centrifugal clutches.

Variator bikes (Peugeot 103, Motobécane 50V)

Variator: Roller weights, contra spring, and starter clutch linings control usable RPM — not the same as a Puch centrifugal bell. Grease variator balls on service; back plate uses a 36 mm left-hand nut on many French bikes.

Chain: Still chain final drive to the rear wheel. Check tension per model — variator cover must be removed for some adjustments.

Carb: Dellorto SHA on Peugeot (O-ring seal critical); Gurtner or Encarwi on Motobécane — jet numbering differs from Bing. See jetting guide and build database.

Centrifugal clutch (Honda Express)

No rider-operated clutch lever for riding. Shoes engage automatically. Inspect for glazing or wear; adjust cables for throttle and choke only.

Chain: Single-speed final drive — tension and lube like any chain moped.