Normal # Light brown, tan or grey firing end.

indicatES that the ENgINE IS RUNNING correctly and general engine conditions are good.

OIL fouling # WET OILY DEPOSITS # LEADING TO WEAK SPARK & MISFIRE.

CAUSE:

Air-fuel mixture too rich # choke stuck on-FAULTY # plug heat range too cold.

CAUSE:

Air-fuel mixture too rich # FAULTY CHOKE UNIT # BLOCKED-DAMAGED AIR FILTER.

Overheating # INSULATER IS BLISTERED-ELECTRODES GLAZED # PRE IGNITION (PINKING).

CAUSE:

ignition timing TO ADVANCED # air-fuel mixture too lean # oil level too low.

plug not tight ENOUGH # plug heat range too hot # COOLING SYSTEM FAULT.

Deposits # electrodes & Insualtor TIP ARE encrusted with a build of deposits - usually LIGHT BROWN in colour.

ENGINE MISFIRE-HESITATION.

CAUSE:

oil leakING through the piston rings or valve seals # due to the wrong oil being used.

EXCESSIVE AMOUNTS OF OIL BEING USED.

Breakage # damage to the insulator TIP # PRE IGNITION (PINKING).

CAUSE:

ignition timing TO ADVANCED # air-fuel mixture too lean # oil level too low.

plug not tight ENOUGH # plug heat range too hot # COOLING SYSTEM FAULT.