[PadG]

Speaking of facts, I have been wrong in regards to the drive shaft sliding on the spline on our bikes

"Normal" drive shafts, such as one on a rear wheel drive truck with traditional rigid axle/leaf spring suspension will slide as the distance changes, like a triangle, but because BMW uses paralever, the distance between splines relative to one another do not change, well not significantly anyway. So the lubing is simply to prevent corrosion.

Thank you. In my response to you, I had said that BMW was sloppy in design to allow partial disengagement of the spline, but what I hadn't said (didn't want to sound like BMW bashing) is that the really sloppy part in the design is to allow any sliding movements at all in load carrying surfaces. Good designer consider this to be quite taboo, IF it's at all avoidable. Take a look at how many generations of people had gone to the trouble of trying to design the "perfect" gear tooth profile so that it achieves perfect rolling action while meshing, instead of sliding action. In practical life, that's impossible to achieve, but we are very close to it. The actual meshing action is mostly rolling (no wears!), but also a little slide.

A glaring example of where sliding action is totally unavoidable is the piston rings sliding on the engine's cylinder wall! That is unavoidable, and if you can find a way around that, you will be very rich! It is the weak point. Look at the Wankel engines. Fantastic power plant, IMHO, but it didn't catch on. Why not? Frequent seal failures! Small seals sliding continuously on a surface.

 

[PadG]

Well, I tried! Continuing to get personal instead of calm logical discussions is no sign of being "friend"! LAF is now going on my "block" list, and I wo't have to look at his personal insults anymore!

BTW, guys, did you know that there is a setting for you to block out certain people? Look for it in your settings.

 

[RRGary]

I am just about ready to do the 12k miles maintenance on my 2021 RT, and I thought that I would share something with the community that should save some money for those who also do their own maintenance. The major differences between the 12k and 6k miles maintenance are that for the 12k miles, you need to change the FD oil, which is extremely simple. Next, you are supposed to change the air filter, which is somewhat of a PITA, since lots of fairing and trims needs to be removed, but otherwise quite simple. Of course, you also have to do the valve clearance check. The last big thing that one is supposed to do is to change the spark-plugs. This last part is what this thread is about!

BMW specifies Iridium spark-plugs for the 1250 boxers. Specifically, the NGK LMAR8AI-10. The very first question that some will ask right away is why change at only 12k miles? That's an iridium plug, and it should last for at least 50k miles! Good question, and partial answer from me is that, it's what BMW specifies, and if you want to make sure that BMW have absolutely no reasons to deny you any potential warranty service in the future, then you should make the change, and keep the old plugs off the bike for future use if they looks to be OK. Keep reading. There some more data on this later.

The next question will come when you start shopping for the specified plug. Wow, why so expensive??? It seems that this plug is only used for the 1250 shiftcam boxers, as far as I can tell. Buying the plug from BMW dealer will cost you more than $30 each, in the US (our friends in the UK and EU countries have it at much lower price). Even Beemerboneyard, who usually have much lower price, is selling them for $54.38 per pair. The best price that I had found was here: Iridium Spark Plug - BMW R1200 2017on R1250; 12 12 8 560 811 / LMAR8AI-10 / NGK for $21.99 each. Can I do any better than this?

Well, in looking around I came across this: NGK LMAR8AI-8. BMW specifies it for the K1600s, and this plug is much cheaper. Best price that I have found was here: NGK 92288 LMAR8AI-8 Laser Iridium Spark Plug at $12.79 each!

So, what is the difference between the 2 plugs, since from the part number, that difference is in the last -10 vs -8. What does that really mean? It turns out that the two plugs are the same plug, with the -10 having the electrode gaped at 1 mm from the factory, while the -8 are gaped from the factory at 0.8 mm. Just for an FYI, here are the meanings of the rest of the NGK part number, specifically as applied to the NGK LMAR8AI-10 :

L- Plug Type Thread Reach: 26.5mm
MA- Metal Shell
R-Resistor
Heat Rating Number 8
A-Firing End Construction Special Design
I-Firing End Construction Single Iridium Spark Plug

Stock Number - 94319
Type - Laser Iridium
Plug Diameter = 10mm
Thread Length = 26.5mm
Hex Nut = 14mm
Heat Range = 8
Resistor = YES

How you use the above information is up to you, as always! It's your bike. However, should you decide to buy the -8 and open up the gap to 1 mm, then I should caution you to be very careful in how you do that. The center iridium electrode is very thin and delicate. You absolutely need to use the proper spark-plug gaping tool to do the job.

Last note is that, I always refer to posts in Adventure Riders Forum for accurate technical information. Those guys are very much more knowledgeable in the technical areas than in any other forums. I had discovered the meaning of the dash-number from there, specifically from this thread: 2019 R1250GSA Spark Plugs/Unicorns? I think that it's worthwhile for you to at least scan over the posts. Now, back to why you might want to consider changing the plugs as early as 12k miles, or at the very least give them a very good examination keeping your riding environment in mind, you need to read post #71 on page 4.

Ride safe!

If you dig deeper, you might find that the reason for the 12k spark plug change out is to keep the bike within smog requirements.
RRGary