LIMBACH L 2400 EF Operating And Maintenance Manual page 36

The electrode gap is 0.7 mm.
Reinstall spark plugs and connect spark plug connectors.
Grease spark plug thread with graphite grease P/N: 170.210.010.
Torque to 20 Nm.
Caution:
Electrodes must always be free from graphite grease! Do not use copper paste.
Use the following spark plugs:
NGK DCPR 7 E
P/N: 250.123.101
Change spark plugs every 200 operating hours.
Note:
The condition of the spark plugs removed from the engine discloses the following
information:
Light grey:
Spark plug and engine adjustment o.k.
Velvet black:
Electrode gap too big
Mixture too rich
Lack of air (induction air filter contaminated)
Engine does not reach required temperature
Oillike glossy:
Interrupted spark plug operation
Excess oil in combustion chamber
Cylinder or piston rings worn out
Pearl formation:
Wrong spark plug
Loose spark plug
Mixture too lean ("false air")
Valves do not close properly
Induction air temperature too high
Edition: 20.06.2018
Operating Manual
L 2400 EF/DF/ET/DT/DX/DS
Page: 36/53