Other Decoding NGK Plugs / Spark Plugs 101

mightymighty2stroke

mightymighty2stroke

I'd rather be on the lake
Location
LKN, NC
Decoding NGK Plugs / Spark Plugs 101

I was looking up some part numbers on NGK’s website and figured I would put them into a table and share. This post includes part numbers for solid tip plugs as well as other useful information on decoding NGK plug part numbers. Might help you decide what to use in a pinch or at the very least help you figure out the myriad of plugs hiding in your truck (wait, is that just me).

Note: NGK Part # helps you decipher what it is. If you go to a parts store, you’ll want to give them the regular part # I have listed. Some parts counter guys can’t cross reference so make it easier for them.


NGK Part # Example: BR8ES

First (Letter) - Thread Diameter. Most (all?) stand ups are "B" (14mm)

Second (Letter) - "R" or No "R". R means there is a 5k ohm resistor in the plug to suppress ignition noise. Plugs with a resistor are recommended in applications with on-board computer systems/GPS/depth finders etc. So this shouldn't really matter in your average stand-up whether or not it has a resistor. Factory superjet calls for one without a resistor.

Third (Number) - Heat Range. The higher it is the colder it is. For example 7 is stock for a 701cc superjet. 8 is a colder plug. 6 is a hotter plug. (Heat Range Explained).

Fourth (Letter) - Thread reach (how long the threaded part is, thus influencing how far down it reaches into the cylinder). Most common for us; H (1/2"), E (3/4")

Fifth (Letter) - Usually an "S" which stands for Standard 2.5mm center electrode


Plugs are available in either solid, removeable nut, or stud tips (tip = spark plug wire end). Solid as it implies is solid and won't unscrew. Removeable nut tips allow you to unscrew the nut on the tip. If you use these in your build you might find that the vibrations make the tips back off, causing loss of spark/poor performance. Stud tips are not used in our applications. If you are searching online you will want to add "solid" to the end of the part number to get a solid tip. E.g. instead of asking for "BR8ES" you want "BR8ES Solid". NGK's part number for a removeable nut tip BR8ES is 5422 and NGK's part number for a solid tip BR8ES is 3961 so there is a difference.

Examples of applying this information:

B7HS - 14mm Thread, no resistor, 7 heat range, 1/2" thread reach, standard 2.5mm center electrode.
BR7ES - 14mm Thread, resistor, 7 heat range, 3/4" thread reach, standard center electrode.

Note: Sometimes you will see a part number followed by -10 or -11. That means 1.0mm plug gap (.040”)/1.1mm (.044”) plug gap (respectively). I did not include these.

NGK Spark Plug Decoder Link

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mightymighty2stroke

mightymighty2stroke

I'd rather be on the lake
Location
LKN, NC
Quinc said:
ADA recommends:
BR8ES or BR9ES spark plugs. Not sure why/which mods would need an 7 vs 8 vs 9.
Click to expand...

You can 'read' the ground strap to see if you have the right heat range. Motor all warmed up, swap in a fresh set of plugs, go for a WOT burst, come back and cut the throttle/coast in. The general rule of thumb is you want the annealing mark (that is the spot where the ground strap changes color) to be in the center of the bend in the spark plug.
 
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Vumad

Vumad

Super Hero, with a cape!
Location
St. Pete, FL
mightymighty2stroke said:
Plugs are available in either solid, removeable nut, or stud tips (tip = spark plug wire end). Solid as it implies is solid and won't unscrew. Removeable nut tips allow you to unscrew the nut on the tip. If you use these in your build you might find that the vibrations make the tips back off, causing loss of spark/poor performance. Stud tips are not used in our applications. If you are searching online you will want to add "solid" to the end of the part number to get a solid tip. E.g. instead of asking for "BR8ES" you want "BR8ES Solid". NGK's part number for a removeable nut tip BR8ES is 5422 and NGK's part number for a solid tip BR8ES is 3961 so there is a difference.
Click to expand...

The solid tops i buy are BR8ES 11. Some auto parts stores carry them, i dont need to order. I want to say its advanced auto parts, but it could be discount.
 
mightymighty2stroke

mightymighty2stroke

I'd rather be on the lake
Location
LKN, NC
BruceSki said:
The Johnson outboard on my boat calls for br8es-11. Pretty sure that determines the gap? It comes gapped differently than a br8es.
Click to expand...

That's right. Some part numbers end in -11 (1.1mm gap) and some in -10 (1.0mm gap). Sometimes those same plugs have solid tops too. lol. The part numbering is a bit confusing. You could just gap them tighter for a stand up.
 
JT_Freeride

JT_Freeride

John Tetenes @Jtetenes
Location
Long Island
Vumad said:
The solid tops i buy are BR8ES 11. Some auto parts stores carry them, i dont need to order. I want to say its advanced auto parts, but it could be discount.
Click to expand...
That gap is way to wide to run on even a stock motor. My gap is more like .01-.02. Few taps on the head or pipe and boom there's your gapping tool
 
Pro-pulsion

Pro-pulsion

Location
Ontario, Canada
Do keep in mind resistor plugs should only be used if there is no resistor in the plug caps. Yamaha states that either B8HS or BR8HS plugs can be used in the stock head with the stock plug boots. If the boots have been changed and there is a resistor built into them you run a risk of creating too much resistance against the CDI and shortening the life span of the capacitors...if not blowing them. When the capacitors are forced to retain voltage or can not discharge it quickly enough they will tend to heat up, swell and eventually burst, it is much like the same situation as rolling over the motor with the plug boots hanging around and no plugs to discharge the coil. The voltage just builds in the CDI until eventual failure. I only ever run non resistor plugs now, that way there is no chance of voltage retention and everything can run them. Also, if you only get the plugs with the removable thread on tips, use red Loc-tite on them if your plug boots require the larger tip. Without any thread locking compound they have a tendency to loosen and back off. Then you have a loose rattling around connection that will really mess with proper ignition and timing.
 
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jo5hi3

jo5hi3

Location
Charlotte NC
Pro-pulsion said:
Do keep in mind resistor plugs should only be used if there is no resistor in the plug caps. Yamaha states that either B8HS or BR8HS plugs can be used in the stock head with the stock plug boots. If the boots have been changed and there is a resistor built into them you run a risk of creating too much resistance against the CDI and shortening the life span of the capacitors...if not blowing them. When the capacitors are forced to retain voltage or can not discharge it quickly enough they will tend to heat up, swell and eventually burst, it is much like the same situation as rolling over the motor with the plug boots hanging around and no plugs to discharge the coil. The voltage just builds in the CDI until eventual failure. I only ever run non resistor plugs now, that way there is no chance of voltage retention and everything can run them. Also, if you only get the plugs with the removable thread on tips, use red Loc-tite on them if your plug boots require the larger tip. Without any thread locking compound they have a tendency to loosen and back off. Then you have a loose rattling around connection that will really mess with proper ignition and timing.
Click to expand...

But running a digital ignition you really need to use resistor plugs. Other wise you will cause other issues.
 
Pro-pulsion

Pro-pulsion

Location
Ontario, Canada
I never thought of that, that is an area that I have no experience with to be honest :) It is good to mention it though, tech info like this helps out everyone. I have not really ever put any thought into digital ignition systems, are they quite popular or getting into the last stop for new hardware? I have had quite impressive results with just my stock CDI and JetManiac coil that changing up my electronics has been pretty well not on my list. I had kicked around a future Advent system but I don't believe that is a digital setup. Either way you have my interest, what are some of the issues that could arise if you don't mind my asking.
 
jo5hi3

jo5hi3

Location
Charlotte NC
I'm not 100% on this but i believe it causes too much noise in the system, so like feedback. Youtube videos of resistor vs nonresistor plugs, if i remember correctly it actually helps lengthen the spark time and the amplitude of it. But its been a while since I did all the research, but there is a good bit of info on the web about it.
 
Pro-pulsion

Pro-pulsion

Location
Ontario, Canada
That's interesting about the feedback. It brings to mind something I was told many years ago about marine CB radios. Apparently the non resistor plugs were norm but because there was no controlled suppression of the spark discharge it created an interference with CB radio waves. It was considered a safety risk by having broken up transmissions should an incident arise, so they pushed for a more widely available correction which became the resistor plugs and plug boots. I never have researched it to validate the claim but I for some reason remember it came from a reliable source which made me have no reason to question it.

As for the MSD boots, I have them on my JetManiac Yamasaki coil which is essentially just an OEM Kawi coil set up for the SuperJet and I only run non-resistor plugs. I have also read that if the caps have resistors and plugs too your spark gets to be quite low reducing the performance of the flame front during combustion. Enhancers I couldn't offer any input on as I just run stock timing, it's amazing what a pipe alone will do for a ski and I am so happy with how my ski performs that I don't really have the desire to change it up any further. I was told by Speedwerx this year though that by running their pipe (which I am) to not use smaller than 37cc domes in my ADA head and no enhancers. There were no comments or suggestions on plugs however.
 
Big Kahuna

Big Kahuna

Administrator
Location
Tuscaloosa, AL
Pro-pulsion said:
That's interesting about the feedback. It brings to mind something I was told many years ago about marine CB radios. Apparently the non resistor plugs were norm but because there was no controlled suppression of the spark discharge it created an interference with CB radio waves. It was considered a safety risk by having broken up transmissions should an incident arise, so they pushed for a more widely available correction which became the resistor plugs and plug boots. I never have researched it to validate the claim but I for some reason remember it came from a reliable source which made me have no reason to question it.

As for the MSD boots, I have them on my JetManiac Yamasaki coil which is essentially just an OEM Kawi coil set up for the SuperJet and I only run non-resistor plugs. I have also read that if the caps have resistors and plugs too your spark gets to be quite low reducing the performance of the flame front during combustion. Enhancers I couldn't offer any input on as I just run stock timing, it's amazing what a pipe alone will do for a ski and I am so happy with how my ski performs that I don't really have the desire to change it up any further. I was told by Speedwerx this year though that by running their pipe (which I am) to not use smaller than 37cc domes in my ADA head and no enhancers. There were no comments or suggestions on plugs however.
Click to expand...
The speedwerx makes great power but you have to be carefull. Keep compression down. Timing at stock setting. If you deviate you risk detonation and seizures ask me how I know. If you are running a programmable ignition the you can get more agressive with your setup.
 
mbrick

mbrick

Location
Los Gatos, CA
Thanks for the helpful table.

I feel like it wasn't completely clear above -- the stock SJ head requires an H length plug, ex B7HS. The longer E length plug (ex BR8ES) can only be used in certain aftermarket heads.
So don't go installing BR8ES plugs into a bone stock engine.

Even though the stock plug is a B7HS 5110, I prefer the BR8HS 6715 because it is a solid top. Otherwise I always apply threadlocker to the removable nut and crank it down tight before installing.
 
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