The Honda ST1100 PanEuropean WebSite  www.st1100.orgNGK SPARKPLUG CODES ====================================

Here is the table of values for NGK spark plug names.

The breakdown is like this: [B] [CPR] [6] [E] [S] - [11]
Six fields.  Some, e.g. the second field, are optional.
Some fields may have multiple letters.

Field one: Thread diameter.
 A = 18mm      B = 14mm        C = 10mm        D = 12mm

Field two: Construction.
 C = hex size 5/8"     K = hex size 5/8 with projected tip (ISO)
 M = compact type      P = projected insulator type
 R = resistor          SD = surface discharge for rotary engines
 U = semi-surface discharge    Z = inductive suppressor

Field three: Heat Range.
 2 = hot, up to 10 = cold.  There's no 1, I guess.

Field four: Thread reach.
 E = 19mm      F = tapered seat
 H = 12.7mm (1.5")     L = 11.2mm (7/16")

 If this field is blank, an 18mm diameter plug has 12mm reach,
 and a 14mm plug has a 9.5mm (3/8") reach.

Field Five: Firing end construction.
 A, B = special design (no details given)
 C = special ground electrode
 G = racing use
 GV = racing use V type
 H = half thread
 K = 2 ground electrodes for certain Toyotas
 L = half heat range
 LM = compact lawn mower type
 M = 2 ground electrodes for Mazda rotary engine
 N = special ground electrode
 P = platinum tip (premium)
 Q = 4 ground electrodes
 R = delta ground electrode for BMW
 S = standard 2.6mm centre electrode
  T = 3 ground electrodes
 V = fine-wire centre electrode, gold palladium
 VX = platinum tip (high performance)
 W = tungsten electrode
 X = booster gap
 Y = v-groove centre electrode

Field Six: (after the dash) Wide gap.
 8 = .032"             9 = .036"               10 = .040"
 11 = .044"             there is no 12          13 = .050"
 14 = .055"             15 = .060"              20 = .080"

Other notes:
There's more, such as for metal shell plugs, "V-Power" plugs
for North American made cars, and other stuff.  I'm not typing it in.

Some Motorcycle-related comments...

Some bikes use the DR8ES-L plug.  Theres's no indication what the 'L'
means; it does not appear in the symbol chart for field six.

Seeing as I specialize in Honda V4 info...

ST1100 (hey, it's a V4) : CR8EH-9
VF1100 : DPR8EA-9
VF1000 : DPR8EA-9
VF750, VF700 : DPR8EA-9
VFR750, VFR700 : DPR9EA-9
VF500 : DPR8EA-9
VFR750R (1990) : CR9EH-9
VFR750F (1990) : CR9EH-9
VFR750F (1991-92) : CR8EH-9

Extended-life platinum tip plugs replacing the CR9EH-9 are
available as CR9EHVX-9.

Resistor plugs are used for two reasons --

 1. They cut down electrostatic interference.

 2. They provide a sharper "edge" to the voltage spike, making for
 a stronger, shorter spark. On high RPM motors, this is important.

The projected insulator simply describes the shape of the plug head.
A projected insulator sticks out a little further into the combustion
chamber.

You can reach NGK at  800-855-8151 (?), 714-855-8278

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