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RM125 spark plug

Big Lenny

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Posts: 13120

Joined: 8/15/2006

Location: Compton, CA USA

10/22/2009 8:51 AM

What are the difference's between that high priced plug Suzuki sells compared the an regular/replacement plug?, that plug is $30..

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Tiki

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Posts: 9970

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Location: Corona, CA USA

10/22/2009 9:04 AM

None other then the Yellow box and the Red S on it. Re-branding costs money.

newmann

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Posts: 14278

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Location: USA

10/22/2009 11:22 AM
Edited Date/Time: 10/22/2009 11:31 AM

No , that's the price of the actual NGK boxed plug, list at $36.99. I will say this though, we ran the original plug in our 01 RM125 for 18 months. It never gave any problems. I believe the fine wire electrode is designed to go with the ignition system on the bike. NGK also make fine wire iridium plugssuch as the BR8EIX/BR9EIX that sell for $10.99 each. Not sure what the differences are between them or for that matter, why the 3 dollar BR8es/BR9ES plugs won't work. Where's Williams at????????????

Chili

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Posts: 788

Joined: 4/1/2008

Location: Winnipeg, CAN

10/22/2009 2:31 PM
Edited Date/Time: 10/22/2009 2:32 PM

That plug was spec'd for some RM and KX125's after they started snapping the electrode and or groundstrap off the regular type plugs, something to do with engine harmonics or something like that. We always used the cheap plugs to get our jetting dialed and than ran the expensive one after that.

Chili

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Posts: 788

Joined: 4/1/2008

Location: Winnipeg, CAN

10/22/2009 2:41 PM

Here is a reply from NGK a few years back when asked the same question by a member at another board I frequent.

"Thank-you for your recent inquiry about the Suzuki RM125 and the recommended spark plugs for this application.

First I would like to explain why the R6918B-8 is so expensive. This particular spark plug was designed and engineered for this specific application. Due to the fact the production volume is lower and the number of spark plugs sold is much lower then that of the BR9ES, the cost of the spark plug is increased. The production costs and the
fact this spark plug utilizes gold palladium, a precious metal the cost is much more.

The Suzuki RM125 is a high revving, high compression engine and has vibration issues throughout the power band. We've tested with Suzuki and found the ES, EG, EV and EGV and determined these spark plugs fail under certain loads and conditions. If you compare the two spark plugs you'll notice a major difference in ground electrode design.
The R6918B has an electrode designed to withstand severe vibration and possible detonation associated with these bikes. A standard spark plugs ground electrode is
welded on the outside of the metal shell and can vibrate like a tuning fork throughout certain rpm ranges. This severe vibration causes fatigue and the ground electrode fails. This is why the R6918B was chosen for this application. The R6918B is very reliable and durable in these conditions. Ignitability with this spark plug is better then the
ES series due to the diameter of the center electrode. Any time you have a racing engine you need to choose a spark plug designed to withstand this type of environment.

I would also like to inform you I am the person who takes care of damage
claims at NGK Spark Plugs. I have had more BR8ES and BR9ES spark plugs
cross my desk every month with broken ground electrodes and receipts for
repairs. When the ground electrode fails it bounces around leaving indentations in the cylinder head and the top of the piston. If your lucky the ground electrode will sneak out of the cylinder, however if your not the
ground electrode wedges itself between the piston and cylinder wall and intern destroys the engine.

I hope I have helped you in better understanding why this spark plug is used in this application. If you have any questions or concerns please feel free
to contact me at (248) 926-6900 ext 248.

Sincerely,

Jon MacQuarrie

Jon MacQuarrie
Technical Customer Service Representative
jmacquarrie@ngksparkplugs.com"

CRFracer117

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Posts: 420

Joined: 12/4/2007

Location: Beaumont, TX USA

10/22/2009 2:43 PM
Edited Date/Time: 10/22/2009 2:49 PM

The one stated for you bike is an R6918B-8 here is the info on what it all means; plug info

Compare it to an BR8EIX

CRFracer117

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Posts: 420

Joined: 12/4/2007

Location: Beaumont, TX USA

10/22/2009 3:04 PM

And here is like side by side comparison of the plugs;
R6918B-7
Racing Plug,
14mm Thread,
19mm (3/4") Reach,
13/16" (20.6mm) Hex Size,
Gasket Seat, Resistor,
Solid Terminal,
Platinum Tipped Fine
Wire Center Electrode,
Angled Ground Electrode,
.024" (0.61") Gap,
Heat Range 7

BR8EIX
Iridium IX Plug,
14mm Thread,
19mm (3/4") Reach,
13/16" (20.6mm) Hex Size,
Gasket Seat, Resistor,
Removable Terminal,
Fine Wire (0.6mm) Iridium Center Electrode,
Tapered Cut Ground Electrode,
.032" (0.8mm) Gap,
Heat Range 8


williamsmotowerx

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Posts: 1435

Joined: 4/1/2008

Location: Saukville, WI USA

10/22/2009 6:38 PM

The high priced plug doesn't have the ground strap fall off and go through the motor when the motor detonates.

Follow me on twitter @williamsmotower if you're a gearhead you'll like the pics, and ask me tech tips.

ratonmacias

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Posts: 320

Joined: 4/1/2008

Location: Guadalajara, MEX

10/23/2009 12:59 PM

and trust me that isnt a myth. i destroyed the cylinder on my 04 rm 125 using a cheap plug after that i got a 144 kit and a bunch of 36 buck spark plugs.

tunedlength

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Posts: 2266

Joined: 12/9/2006

Location: Ontario, CA USA

10/23/2009 7:21 PM

I cant get over the thorough reply from NGK.
Thats service!

Ozzy

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Posts: 882

Joined: 4/1/2008

Location: USA

10/23/2009 11:31 PM

"I cant get over the thorough reply from NGK.
Thats service!"..........

DITTO.
Dave O.

Big Lenny

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Posts: 13120

Joined: 8/15/2006

Location: Compton, CA USA

10/24/2009 11:01 AM

williamsmotowerx wrote: The high priced plug doesn't have the ground strap fall off and go through the motor when the motor detonates.

Tha's the first thing I looked at when I compared the two, there was a difference, bike had the cheap-o in there, does it affect the way the bike runs also?..Thanks fellas...

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Chili

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Location: Winnipeg, CAN

10/25/2009 6:32 AM

I can't say I ever noticed a difference in how it ran between the plugs. We always dialed the jetting with the EG plugs and then switched to the spec'd plug after that for the peace of mind.

williamsmotowerx

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Posts: 1435

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Location: Saukville, WI USA

10/25/2009 12:12 PM
Edited Date/Time: 10/25/2009 12:13 PM

Chili wrote: I can't say I ever noticed a difference in how it ran between the plugs. We always dialed the jetting with the EG plugs and then switched to the spec'd plug after that for the peace of mind.

Chili's right. Doesn't affect the way it runs.

Usually fine to dial it in with cheap plug. But limited use!

I can actually modify the heads so you don't need to run the expensive plug.

Follow me on twitter @williamsmotower if you're a gearhead you'll like the pics, and ask me tech tips.

queen of spodes

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Location: Atlanta, GA USA

10/25/2009 5:31 PM

williamsmotowerx wrote: Chili's right. Doesn't affect the way it runs.

Usually fine to dial it in with cheap plug. But limited use!

I can actually modify the heads so you don't need to run the expensive plug.

motowerx what does this cost?

williamsmotowerx

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Posts: 1435

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Location: Saukville, WI USA

10/25/2009 5:38 PM

Shoot me an email for price, jesse@williamsmotowerx.net

Follow me on twitter @williamsmotower if you're a gearhead you'll like the pics, and ask me tech tips.

JGPenfield

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Location: Terrell, TX USA

9/12/2011 7:26 PM

Chili wrote: I can't say I ever noticed a difference in how it ran between the plugs. We always dialed the jetting with the EG plugs and then switched to the spec'd plug after that for the peace of mind.

williamsmotowerx wrote: Chili's right. Doesn't affect the way it runs.

Usually fine to dial it in with cheap plug. But limited use!

I can actually modify the heads so you don't need to run the expensive plug.

Why would one pay to have a head modified so you can save 26 dollars on a spark plug?

mxtech1

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Posts: 532

Joined: 7/21/2011

Location: Galesburg, IL USA

9/13/2011 5:32 AM

It's pretty cut and dry, obviously NGK has done their research correctly and even gave a very thorough explanantion in the post above. Why would you consider running anything but?? Sure, it sucks to drop over 30 bucks on a spark plug, but when you're jetting is dialed in that plug is easily going to last you over a season.

I've ran standard plugs, iridium, and NGK's "super plugs" through several RM trials using an exhaust sniffer hooked to PC graphing software to see burnt fuel mixture ratios. The data didn't lie. The standard plugs burnt the least efficient, while the "super plug" burned the most efficient. This was a controlled test where jetting was spot-on from dyno runs and a consistent race fuel was used. The only difference was plug swapping. I actually saw a big of a difference as 3.5% parts per thousand of unburnt fuel through the exhaust sniffer between the cheapest and most expensive plug.

I also found the mid-line iridium series plugs burn't virtually to the same specs as the super plugs. The iridium seems to be a great compromise between the two, since it's only $10-15, but mind you it also is like the standard plug because it does not have the fail-safe design to prevent breakage during failure, potentially to damage the engine. I run the iridium series in every engine i build, besides any RM's.

In my mind, i've always thought of the $30 plug as cheap insurance as one more thing I can eliminate that could potentially damage my engines.

mxtech1

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Joined: 7/21/2011

Location: Galesburg, IL USA

9/13/2011 5:40 AM

Chili wrote: I can't say I ever noticed a difference in how it ran between the plugs. We always dialed the jetting with the EG plugs and then switched to the spec'd plug after that for the peace of mind.

williamsmotowerx wrote: Chili's right. Doesn't affect the way it runs.

Usually fine to dial it in with cheap plug. But limited use!

I can actually modify the heads so you don't need to run the expensive plug.

How can modifiying the head reduce engine vibration? Because the main principle behind these plugs is the concept that they are built stouter to prevent breakage from vibration.

Maybe you should try selling him off on your blueprinting and balancing instead of a squish-band reshape to compromise the compression ratio.

One could possibly argue that changing the compression ratio could reduce some internal stress on the engine, but thats merely putting a band-aid on a wound that needs stitches. the real problem of the RM engines is the extreme vibration caused by some not so perfect engineering.
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