Honda CT90 / Trail 90 Spark Plugs

Spark plugs are available in various heat ranges. Select plugs from a heat range that suits the load and temperature conditions under which your bike will be run. As a rule of thumb, use the highest numbered plug that will not foul.

We recommend the D8HA (NGK) Spark plug

Spark Plug Gap Specification: 0.6 - 0.7 mm (0.024 - 0.028 in.)

Adjusting the Plug Gap:

Modify the gap by bending only the outer negative electrode. Use a Spark Plug Gap Gauge to ensure the spacing is accurate.

Removing Spark Plugs:

1. Clear out any debris from the spark plug wells to prevent it from falling into the cylinders when the plugs are removed.
2. Carefully detach the coil leads—avoid pulling too hard, as this could separate the wires from the insulator boots.
3. Use an 18mm spark plug socket to unscrew and remove the plugs.

Inspection:

A spark plug tip should typically appear in shades ranging from light tan to chocolate brown. If reusing old plugs, inspect them for any buildup on the electrodes, cracked insulators, damaged threads, or electrode erosion. If even one plug is faulty, replace the entire set.

• Abnormal Tip Conditions 

• • Black Carbon Deposit 
    • Fuel mixture too rich
    • Dirty air filter
    • Prolonged ideling
    • Low heat range
  • Oil Fouling (Wet Tip)
    • Worn pistons or rings
    • Timing off
    • Loose plug
    • Worn valve guides
  • White Crust
    • Fuel mix too rich
    • Timing off
    • Loose plug
    • Hot heat range

Cleaning :

You can clean your spark plugs with a simple wire brush and solvent.