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MOTRS

Cosmo Sport (110S)

1967-1972 / Coupe / Japan

All Cosmo Sport (110S) problems All workshop issues
Minor Ignition System

Spark Plug Fouling

Symptoms

Misfiring, rough idle, loss of power. Plugs come out with heavy carbon or oil deposits.

Cause

Rotary engines are harder on spark plugs than reciprocating engines. The combustion chamber sweeps past the plug, and the plug tip is exposed to the oil that lubricates the apex seals. Short trips and cold running exacerbate fouling. The 10A's relatively low compression (by modern standards) means incomplete combustion is more likely.

Fix

Use the correct spark plug (NGK BP6ES or equivalent, check a Cosmo Sport-specific reference).

Replace plugs at shorter intervals than you would for a piston engine, every 10,000-15,000 km.

Ensure the oil metering pump is not over-delivering.

A hotter plug grade may help if the car is used for short trips.

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// More Cosmo Sport (110S) problems

Other known issues

Common Ignition System

Points and Condenser Degradation

Misfiring, rough running, difficulty starting, inconsistent idle.
Minor Engine, 10A Twin-Rotor (982cc)

Apex Seal Wear

Loss of compression, reduced power, difficulty starting (especially when cold), blue-white exhaust smoke, and eventually misfiring and inability to idle. A rotary engine with worn apex seals is an engine that needs a rebuild, there is no halfway measure.
Common Engine, 10A Twin-Rotor (982cc)

Hard Cold Starting

The engine cranks extensively before firing when cold. May require multiple attempts. Once warm, starting is normal.
Minor Engine, 10A Twin-Rotor (982cc)

Oil Metering Pump Failure

Without lubrication, the apex seals run metal-on-metal against the rotor housing. Wear accelerates catastrophically. The engine may seize.
Critical Engine, 10A Twin-Rotor (982cc)

Cooling System Inadequacy

Engine overheating, particularly in traffic or on hot days. The temperature gauge climbs steadily, coolant may boil over, and in extreme cases the engine suffers heat-related damage (warped housings, blown coolant seals).
Common Fuel System

Carburettor Deterioration

Poor idle, flat spots during acceleration, fuel leaks, difficulty starting, rich or lean running.
View all 10 Cosmo Sport (110S) problems