R1250GSA - Spark Plugs

Anyone know the reason BMW switched from the LMAR8D-J plug to the LMAR8A1-10 plug Same heat range, thread length ?

Change from standard electrode to fine-wire iridium electrode?

105258 said:

Anyone know the reason BMW switched from the LMAR8D-J plug to the LMAR8A1-10 plug Same heat range, thread length ?

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According to the NGK documentation, the LMAR8D-J is good for 30k miles, the Iridium plugs are rated for 100k miles. The change in plug type was probably related to emission regulations. Note: the -10 denotes a plug gap of 1mm. The Iridium plug for the 1200LC has a -8 so the plug gap is .8mm. The larger gap of the -10 plugs requires a higher voltage to arc across the larger gap. The stick coils for the R1250 may be different than the ones for the R1200. (one would have to check the part numbers) If they are different, I would only use -8 plugs in a R1200. The larger gap of the -10 plugs could shorten their life span.

Great info

thanks I will check part no but if they last 100000km then they are worth the extra cost.

b_rubenstein said:

The Iridium plug for the 1200LC has a -8 so the plug gap is .8mm. The larger gap of the -10 plugs requires a higher voltage to arc across the larger gap.

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Are you sure? I think the "8" is the heat range, and the "-J" is equivalent to a "-10"... (J is 10th letter of alphabet)

So, I think the difference is that the "D" plug is traditional (dual?) electrode, and "AI" is the Iridium plug.

105258 said:

thanks I will check part no but if they last 100000km then they are worth the extra cost.

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I use iridium plugs in my wethead... but don't expect them to last 100,000 kilometers. The dual electrode LMAR8D-J will be pretty shot at the 20,000 kilometer service. I use LMAR9AI-10 iridium plugs, and I find that they last a bit longer, and are easier to find from online retailers. But I still changed my last set at 8000 miles, and noticed a slight improvement in high-rpm smoothness.

Lately, I have difficulty finding any LMAR8D-J plugs, and the price is in the $20 per plug range. The iridium LMAR9AI-10 is readily available, and about half the cost. Note that it is 1 range cooler, which works well in my RT. I found the LMAR8AI-10 on eBay, but again it seems to be in scarce supply, although cheaper than the dual electrode version.

The LMAR9AI-10 is also available direct from NGK

The 1200 plug would be the LMAR8BI-8
The 2 plugs differ by the preset gap 1mm vs .8mm and the heat range (higher number is cooler)

azgman said:

The 1200 plug would be the LMAR8BI-8

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I am unfamiliar with that plug. Can you provide a fitment reference? I was assuming we were talking about a 2013-2018 R1200, either a GS or an RT.

Thanks, cap