NGK sparkplug codes

Here is the table of values for NGK spark plugs. not all of them have the - number on the end.

The breakdown is like this: [R] [6] [H] [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"

Re: NGK sparkplug codes

that is very nice info. I hate to rain on your parade but a little more visually pleasing look at it is here.

and in the wiki. i came across it the other day tryin to find the difference between B5HS and BP5HS. and the key tells you. good topic for future reference

Re: NGK sparkplug codes

Lance applewhite /

Thanks warisesi,

I'll put this in shoe box with Freds guide

Re: NGK sparkplug codes

when you have dialup waiting for a pdf takes forever also if people are here they can look here without added pleasing visuals.

Re: NGK sparkplug codes

this is true.

Re: NGK sparkplug codes

at the shop I used to work at we had a NGK cross reference guide for all makes and models. One of the sections was for mopeds and down both pages it just said B6HS or B5HS, kinda funny.

Re: NGK sparkplug codes

Also i didnt post before i now only use champion because the heat ranges is sort of the same as NGK but a little off and they have more extension on the tip so i find they burn a bit better in my cadys and mobys.

The so called equivalent listed for champion is

L86C = B6HS

L82C = B7HS

L78C = B8HS

Re: NGK sparkplug codes

haha ive seen that same book. i doubt they put any consideration into the plug choice, they are ALL b5hs or 6hs.

wari.. question for you. do you know the difference between b5hs and bP5hs? According to the chart, P stands for projected insulator. When you look at the plugs, you can definitely see the difference. A b5hs porcelain part barely sticks out, while the P sticks quite a bit out.

What complications/problems could the projected tip type cause? I've been running one on my moby for a while and im not sure if it's causing my backfiring-esque problems. I switched to an l86c cause it doesnt have the projected tip, but I'm not sure if it made a difference.


Re: NGK sparkplug codes

the B5HS is standard length and the BP5HS is projected which means the cernal of the explosion is deeper in the combustion chamber. The heat range is the same tho. If you put a B6HS and a BP6HS wif a L86C champion in the middle then you notice the champion is actually longer then the normal ngk but shorter then the projected ngk..

when you get the right range then you can fool with projection. the actual electrode part of the spark plug tells the detail if you are exact. it is splitting hairs at that point but after a lot of long hard runs you can see the one that is still firing clean and which one is blistering a bit near the porcelin or getting soot near the porcelin.

Re: NGK sparkplug codes

mhmm.. ok. thanks, that helps. when you say blistering? does that look anything like attached picture? (i know, another paint picture, but hey, it works). its got a shiney blackish brown spot in one concentrated area on the ceramic.

i get shitty backfiring sounds (not confirmed yet that they are backfiring, cause i dont know exactly what backfire sounds like) at top speeds and it sucks. i dont know if its timing or plug or both or something altogether different.


Re: NGK sparkplug codes

good picky from the description maybe you are in the right range but you need to adjust the timing a little retarded. then try working with projection.

Re: NGK sparkplug codes

thank you wari, always very helpful. timing will do. thing is, must find time to adjust timing!

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