This page summarises the procedures in the Sinclair C5 Owner's Handbook (Sinclair Vehicles, 1985; 38 pp.). Page numbers refer to the handbook. “Left” and “right” are as seen from the driving seat. Figures are from the handbook unless a note says otherwise.

1. Steering bars, under the knees
2. Front brake lever (right hand)
3. Rear brake lever (left hand)
4. Parking brake locking lever
5. Power switch, under a rubber moulding on the left hand grip
6. Instrument pod
7. Master security switch, which fits into the battery cover
8. Cut-out button (red, on the master switch)
9. Lamp switch, on the left-hand front edge of the seat
10. Pedals; 11. Drive chain

12–13. Boot lock and boot; 14–15. Front and rear lamps; 16. Front wheel cover

1. Battery securing straps; 18. Vehicle serial number plate; 19. Central tunnel; 20. Lifting points

The battery goes in the left foot well, terminals towards the centre and the switch aperture facing forward. The supplied tools are a vehicle support (jack tube), a battery securing nut and hub cone spanner, and a wheel nut spanner.

It's worth practising the switch sequence off the vehicle before fitting it.

• Press the red cut-out button to switch off the motor circuits. The key springs from D back to P.
• Never turn the key by hand from D to P, and never use the cut-out to control speed.
• If you'll leave the C5 unused for a week or more, take the master switch off the battery. The instruments draw a small current all the time.
• Whenever neither the switch nor the charger plug is in the battery cover, fit the contact cover.

Mechanical

• Tyre pressures.
• Pedalling forwards moves the vehicle; pedalling backwards doesn't. Pushing the vehicle forwards doesn't turn the pedals.
• The front wheel points straight ahead when the bars are at right angles to the tunnel.
• Both brakes and the parking lock work.

Battery installation

• Electrolyte should sit 6–10 mm below the lip. Top up with distilled water.
• Put a light smear of petroleum jelly on the terminals and nuts. Tighten the cover nuts finger-tight, then one more turn with the tool.

Electrical

• Chock the front wheel. Lift the left rear at the lifting point onto the vehicle support.
• At P, check the lamps. At D, check the pod, then press the power switch. The left rear wheel should turn.

• Moving off: release the parking brake and press the power button. Use the pedals to help when starting, because that's when the battery and motor are most loaded.
• Speed control: pulse the button and coast. Power up to the speed you want, let go, coast, and repeat.
• Slowing: release the power switch first. Don't brake against the motor.
• Stopping distances from about 12 mph:

• Hills: always pedal going uphill. Going downhill, brake in bursts rather than continuously, so the brakes don't overheat. (The front rim can soften; see Known Problems and Fault Finding.)
• Reversing: the motor only drives forwards. You can push the C5 backwards, but no faster than a slow walk, or the drive (and the control box diode) can be damaged.
• Parking brake: squeeze the rear lever and push the lock to the right. It acts only on the right-hand rear wheel. On a slope, chock a wheel as well.
• Towing: never tow a C5 or tow with one. Carry it on a trailer, in a van or in an estate car.
• Boot: maximum 10 kg. Don't drive with the boot open.

Left display: motor load. Green means low current, yellow medium, red high. When starting off, aim to pedal the display up into yellow and then green. Staying in green gives the best range.

Right display: battery condition.

• It measures discharge starting from a full battery, and resets every time the master switch is reconnected. Always reconnect to a fully charged battery.
• Segments go out one at a time until only the left red one is lit.
• If you keep using power on the last red segment, it flashes, the buzzer sounds, and 20 s later the power is cut. This protects the battery from deep discharge.
• The lamps keep working after a motor cut-out.

• The battery is an Oldham C5 battery: 6 cells, 36 Ah nominal, lead-acid. The charger is matched to it and the handbook says to use no other charger and no other battery.
• The charger runs on 220–240 V AC and is double-insulated (no earth needed). It has a 13 A plug with a 3 A fuse. Nothing inside can be repaired by the user; if a lead is damaged, replace the whole charger.
• Connect the charger to the battery before switching on at the mains. Switch off at the mains before disconnecting.
• Lights: red = charging; green = full. Leaving it on after green does no harm.
• Charging time from the cut-out point is about 8 hours. The handbook's chart shows roughly 20 % after 1 h, 40 % after 2 h, about 60 % after 3 h, 80 % after 4 h, 85 % after 5 h, 90 % after 6 h, 95 % after 7 h and 100 % after 8 h.
• During the last 4 hours the battery's internal chemistry changes. Charging regularly beyond 80 % is essential for its life.
• Put the C5 on charge after every use. Charge it monthly even when it's not being used.
• Topping up: at least weekly, with the battery fully charged. Shake out gas bubbles first, then fill to 6–10 mm below the lip. Don't overfill.
• A new battery improves over its first few journeys, then fades to perhaps 80 % of its peak after a year of steady use.
• Safety: the battery gives off explosive gas, so no flames or sparks near it. Take off jewellery before handling it. Don't let anything metal near the terminals or the switch aperture. For acid spills, neutralise with washing soda or bicarbonate, one tablespoon per pint of warm water.

Before calling an engineer, check: battery charged; connections tight; chain on; any cut-out given time to reset; master switch seated and in the right position; charger lead unplugged from the vehicle; brakes adjusted; tyres inflated.

Sinclair recommended a professional service every six months.

• Wash with warm soapy water. The polypropylene doesn't need wax or polish; scrub textured areas with a stiff brush.
• Store somewhere dry and ventilated, and charge the battery monthly.

• 30 psi front, 35 psi rear. Use a foot or cycle pump, not a garage air line.
• The front valve is behind the snap-on wheel cover. The rear valves are reached from under the boot.
• If a tyre is very soft, take the weight off it with the vehicle support before inflating, so the tyre seats properly.

• Block-to-rim clearance should be 1.5–3.0 mm. Adjust with the adjuster and locknut; if you run out of adjustment, pull more cable through at the cable bolt.
• Replace the blocks in pairs when they're worn to within 3 mm of the metal shoe.
• No part of a block may touch the tyre.
• Torque the blocks to 4 Nm.

• Raise the right rear wheel. Turn the adjuster until the shoes just drag, then back it off until the wheel spins freely. Never adjust so far that you can't turn the wheel by hand.
• Wear check: compare the angle of the operating lever to vertical with the brake on, and again with the cable bolt released. If the “on” angle is the same as or more than the “free” angle, the linings need replacing.

• Oil them where they leave the outers, every six months.
• Replace inner and outer as a complete unit if there's any fraying. Route and clip them as in the handbook's fig. 38; this needs the C5 stood on end with the battery removed.

• Front bulb: pull the protective box at the front of the central tunnel off its grommets and pull out the holder.
• Rear bulb: remove the lens screws.
• Bulbs are 12 V 5 W wedge, type W10/5. Keep a spare.

• Remove the boot. Run a thin film of light oil along the chain, then wipe off the excess.
• Strip and clean it once a year.
• If the chain comes off, you can reach it at the front by removing the access covers, or at the rear by removing the boot. Refit the chain tensioner as shown in the handbook.

• Deflection midway between the pulleys should be 1.5 mm (1/16″) under finger pressure.
  • Too tight: bearing wear and friction (and, in practice, motor tilt and pinion wear).
  • Too loose: belt wear and slipping.
• Refitting a slipped belt:
  1. Remove the boot.
  2. Loosen the motor mounting bolt.
  3. Rotate the eccentrically-mounted motor to bring the pulleys closer, and slide the motor about 40 mm clear of the drive wheel.
  4. Put the belt over the drive pulley, then feed it onto the motor pulley as you slide the motor fully back to the left.
  5. Rotate the motor until the deflection is 1.5 mm.
  6. Tighten the clamp bolt to 8 Nm. Don't over-tighten; it damages the motor mounting.

• Check: front brake on, rock the C5. There should be no play.
• Adjust: remove the front lamp. Slacken the locknut and turn the ring until the steering binds, then back it off 1/6 turn and lock it. Head bearing locknuts are torqued to 42 Nm.

• Remove the bar cover and unplug the power switch wiring (plus indicator and horn wiring if fitted; the connectors are under the tunnel). Unclip the brake cables and pull them through the grommet.
• Loosen the steering stem nut 1½–2 turns, tap it to free the internal collar, and twist the column up.
• Adjust as for the head bearing.

• The bars must be level, with their underside 15–20 mm above the central tunnel. The “STOP” mark on the stem must never show above the tunnel.
• With the wheel straight, the bars must be at right angles to the tunnel.
• Torques: stem nut 11 Nm, bar clamp nut 8 Nm.

• Use a crank puller to remove the crank. Adjust the setting ring until the spindle just binds, back it off until it turns freely, then lock it. The lock ring is torqued to 37 Nm.
• Sinclair advised having this checked yearly.

• Front: cup-and-cone. Tighten until the spindle binds, back off until it just turns freely, then lock.
• Right rear: tighten the outer cone until the wheel just turns freely, then lock.
• The left rear needs no adjustment.

• Front: remove the wheel covers, slacken the brake, and undo the wheel nuts (22 Nm on refitting).
• Left rear (driven): prise off the cap and remove the bolt and washer (25 Nm).
• Right rear: prise off the cap, undo the locknut, and remove the outer cone with a cranked spanner. Watch out for the loose bearings. Refit the locknut at 25 Nm and re-adjust the bearing.
• The wheels need no maintenance, and the handbook says only C5 wheels should be fitted.

• Open the boot and pull the two retaining clips down off their bosses. Spring the wheel arches outwards and lift the boot away.

• Remove the boot, undo the control-box cover screws and take care of the weather seal.
• Main fuse 5 A is on the right-hand side; auxiliary fuse 1 A. Both are glass, 20 mm long.
• If a fuse keeps blowing, look for damaged wiring or a faulty bulb.

• Use standard tyre-lever and patch technique, and carry three tyre levers and a repair kit.
• Re-seat the tyre so it sits concentrically on the rim before inflating fully.

You could: drive with no licence, tax, insurance, number plates or helmet, at 14 years or older.

You could not:

• drive on pavements, footpaths or motorways;
• fit a non-electric motor, or one over 250 W nominal;
• remove the pedals;
• go faster than 15 mph under power;
• fit non-specified brakes, a different battery or non-compliant lighting;
• remove the vehicle identification plate.

See Legislation for how the law has changed since 1985.

• Vehicle: 12 months, first owner, UK only, handled by Hoover Service Offices.
• Battery: the maker's own 12-month warranty, through Sinclair Battery Centres.
• Excluded: hire use, competition, off-road use, non-Hoover/Sinclair parts, and wear items (tyres, tubes, belts, cables, brake linings, bulbs, fuses, chain, pedals).
• Sinclair Vehicles Ltd's address in the handbook: Stanhope Road, Camberley, Surrey GU15 3PS; tel. 0276 686262.

• Sinclair C5 Owner's Handbook, © Sinclair Vehicles 1985. Scanned copy on c5owners.com (Resources › Original Documents › Owners Handbook).