Spark plugs for '04 K1200GT

[corey61]

I'm gathering parts for the 24k mi service on my '04 K12GT. Last time I replaced them (Sept 2019) the original Bosch XR7LDC plugs could be found at a reasonable price (I paid $6.25 ea. at that time.) Now, I'm having a hard time with that. I can find the BMW OEM plugs but they are ~$19 ea. Hard to stomach, that...

Time to look at alternatives. I found the cross-reference (i.e., list of alternatives) below. And the shop I bought the XR7LDC's from three years ago now offers the NGK DPR7EA-9 replacement... at a low, low price of $3.66 ea.

I'm a bit wary of this. So... anyone have a suggestion/recommendation for a worthy replacement for the Bosch item? Or know where to source the Bosch genuine article at a sane price? Am I over-thinking this and the NGK plugs are just fine...??

 

[gregfeeler]

I'm gathering parts for the 24k mi service on my '04 K12GT. Last time I replaced them (Sept 2019) the original Bosch XR7LDC plugs could be found at a reasonable price (I paid $6.25 ea. at that time.) Now, I'm having a hard time with that. I can find the BMW OEM plugs but they are ~$19 ea. Hard to stomach, that...

Time to look at alternatives. I found the cross-reference (i.e., list of alternatives) below. And the shop I bought the XR7LDC's from three years ago now offers the NGK DPR7EA-9 replacement... at a low, low price of $3.66 ea.

I'm a bit wary of this. So... anyone have a suggestion/recommendation for a worthy replacement for the Bosch item? Or know where to source the Bosch genuine article at a sane price? Am I over-thinking this and the NGK plugs are just fine...??

I have a 2003 K1200RS. Where did you get this cross reference chart, and why are you warry of the NGK DPR7EA-9 alternatives?

 

[drneo66]

Looks as if the Bosch model was discontinued, which could explain why they are difficult to find:

https://www.euromotoelectrics.com/product-p/xr7ldc.htm


NKG does come stock on many bike manufactures, so I wouldn't be too warry

https://www.euromotoelectrics.com/category-s/1782.htm

Another alternative depending on your year:
https://www.beemerboneyard.com/sparkplugs.html


I personally have not found any mileage/performance differences with running Iridium vs standard spark plugs.

 

[corey61]

I have a 2003 K1200RS. Where did you get this cross reference chart, and why are you warry of the NGK DPR7EA-9 alternatives?

Here's the link:
https://www.sparkplug-crossreference.com/convert/BOSCH_PN/XR7LDC

... And I'm wary of the NGK plugs for no reason other than that they're really inexpensive. The BOSCH OEM plugs I bought, when they were still available, were ~2x the price, same supplier.

Whaddya think - am I over-thinking this? You can be frank!
I know there are seasoned wrench-turners on this forum who are very particular about key components... like spark plugs. Thought there might be some informed opinions....

 

[corey61]

Looks as if the Bosch model was discontinued, which could explain why they are difficult to find:

https://www.euromotoelectrics.com/product-p/xr7ldc.htm


NKG does come stock on many bike manufactures, so I wouldn't be too warry

https://www.euromotoelectrics.com/category-s/1782.htm

Another alternative depending on your year:
https://www.beemerboneyard.com/sparkplugs.html


I personally have not found any mileage/performance differences with running Iridium vs standard spark plugs.

Yes... euromotoelectrics is exactly the supplier I was referring to who offers the NGK plug I mentioned in the OP. They're also who I bought the Bosch OEM plugs from, three years ago...
They show the NGK DPR7EA-9 as the replacement for the BMW OEM part no. here.

 

[gregfeeler]

Here's the link:
https://www.sparkplug-crossreference.com/convert/BOSCH_PN/XR7LDC

... And I'm wary of the NGK plugs for no reason other than that they're really inexpensive. The BOSCH OEM plugs I bought, when they were still available, were ~2x the price, same supplier.

Whaddya think - am I over-thinking this? You can be frank!
I know there are seasoned wrench-turners on this forum who are very particular about key components... like spark plugs. Thought there might be some informed opinions....

I appreciate the offer to be Frank, but I think I'll stick with Greg. Seriously, I believe you are over thinking this. NGK has made quality sparkplugs (and many other things) since at least the 1960's. There are many factors driving price of parts like sparkplugs, but in the end they are really stone simple devices. As long as the tip meets any special requirements from the engine designers, which is NOT the case for classic K-bike brick motors, then the key variable is heat range, and that is determined by the mechanical construction of the plug. I've used NGK plugs many times over the years and found that they are about a quarter of a step off from Bosch, but never enough to affect performance or plug life, and in some cases were a better fit than the Bosch plugs. YMMV.

 

[98lee]

As long as the tip meets any special requirements from the engine designers, which is NOT the case for classic K-bike brick motors,

Greg,

What have you found in regards to the classic brick motors? I’ve always used the X5DC plugs and not ever thought much more about them.

 

[gregfeeler]

Greg,

What have you found in regards to the classic brick motors? I’ve always used the X5DC plugs and not ever thought much more about them.

That's what I've used and they work so well I don't have to think about them either. But, I have used NGKs in other bikes and cars with good results. Overall, my experience with spark plugs is to stick with the OEM brand and type whenever you can. If they are not working out, then you likely have some other problem. If you can't get the OEM, then there should be suitable alternatives, but after the first time you switch it's good to run them a while and then take one or two out to check for condition.

 

[pauls1150]

I'm continually amazed, and a bit disappointed, by the number of people who insist that they must absolutely use the "factory-recommended" parts.
I've never had a bad NGK plug in over 50 years of riding bikes from various continents.
I've never had a bad Autolite plug.
I have had the occasional bad Champion plug.
I have swapped out an occasional "Harley-Davidson" plug (wonder who actually makes them?).
I have had the occasional bad Bosch plug; my own experience convinces me that NGKs ignite better anyway.

 

[gregfeeler]

I'm continually amazed, and a bit disappointed, by the number of people who insist that they must absolutely use the "factory-recommended" parts.
I've never had a bad NGK plug in over 50 years of riding bikes from various continents.
I've never had a bad Autolite plug.
I have had the occasional bad Champion plug.
I have swapped out an occasional "Harley-Davidson" plug (wonder who actually makes them?).
I have had the occasional bad Bosch plug; my own experience convinces me that NGKs ignite better anyway.

To be clear, like you, I've used a lot of different plugs in all kinds of engines and all have been "good". However, sometimes a given brand and plug model has a heat range that don't have an exact match in another brand. My larger point is that I prefer to use the OEM specified plug(s) provided that I can get them at a reasonable price. But, you are not going to hurt anything if you use a cross-referenced major brand alternative.

 

[98lee]

I know one thing that is different about the early bricks, specifically the K75s. Instead of resistance built into the wires, they use an air gap in the wire. If you would do a typical resiatance check of those wires, you would declare them bad. So there is two gaps that the secondary spark must jump per cylinder (wire gap and plug gap). Putting resistance plugs in those bikes can cause problems. I could see a case where a cross referenced plug that would work fine in a normal system might not perform optimally in the two gap system.

I don’t know why BMW designed the system that way. Nor do I imagine that I am smarter than the engineers that designed some of these systems, but it seems if they can design something overly complex, they will do it.

 

[AntonLargiader]

Has anyone experienced firsthand the idea that Bosch has discontinued the XR7LDC?

People said this in the past about the W5DC and the reality was just that aftermarket suppliers couldn't get them. This was many years ago and I still have never had an order for W5DC plugs go unfilled from BMW.

 

[corey61]

Has anyone experienced firsthand the idea that Bosch has discontinued the XR7LDC?


Anton,

Right. I can definitely order the BMW OEM spark plugs (that are really the Bosch XR7LDC) - BMW P/N 12121465104 - to the tune of $19.26 ea., plus tax. Last time I changed plugs was 3 yrs ago, and I was pleased to learn about, and order, the Bosch plugs (them being the identically same item) from an aftermarket source. For less than a third the price. That option appears to have evaporated, hence my question.

Just like people wax vigorously and long about the benefits of particular engine oils, gear oils, brands of gasoline, and so on... so, too, I reasoned, might there be a chorus of opinions about spark plugs. I mean, they're kinda essential, no...?

So it came down to:
Bosch XR7LDC: no question, no doubt. These are the white-labeled BMW plugs. Done deal.
Any other alternative: not so sure.

But, Greg-not-Frank assures me that the NGKs will be fine and when I invited him to tell me I'm over-thinking, he happily obliged. So... Here we go.

Cheers.

 

[corey61]

...I've used NGK plugs many times over the years and found that they are about a quarter of a step off from Bosch, but never enough to affect performance or plug life, and in some cases were a better fit than the Bosch plugs. YMMV.

Care to elaborate on quarter of a step off? Thanks.

 

[corey61]

I personally have not found any mileage/performance differences with running Iridium vs standard spark plugs.

That's not terribly surprising to me. The claims I read about just exactly WHY iridium plugs should enhance performance are, well to be frank... specious. I see claims like:

You will notice a major improvement to the acceleration profile of the gasoline vehicles when you go for iridium spark plugs. This change comes from the fact that the gasoline vehicles responds faster to the throttle operations.

The spark plug manufacturers are unanimous about the fact that iridium spark plugs can considerably improve the engine power.

With these high performance spark plugs vehicle get improved combustion...

Those three little gems of non-physics-based non-information come from... wait for it... NGK.

Sure, iridium plugs will last longer. May be worth the extra price. YMMV. But improved combustion? Not so much, I don't think.

At the risk of coming off as smug or pretentious, this is probably where I should mention that I have a doctorate in Mechanical Engineering. And my PhD research, 30 years ago, was in combustion. So, I could tell you exactly why those claims are specious.

Or not.

Cheers.

 

[AntonLargiader]

I think it's a bit sleazy for a vendor to say that a product is discontinued by the manufacturer (mentally pushing customers to seek an alternative) if in reality it's only unavailable from that vendor. BBY did not try to tell us that Brembo products had been discontinued by Brembo when in fact Brembo had only stopped selling to BBY. Of course, BBY didn't have an alternative to sell so there was no motivation to say that.

I will ask my dealership next week if they know anything about a discontinuation of the XR7LDC plug.

 

[gregfeeler]

Care to elaborate on quarter of a step off? Thanks.

"A quarter of a step off" ways my way of saying that I've seen plugs which were listed as cross-overs for each other run at different temperatures in practice. This was common during my 2-stroke bike days, but I've also seen it with carbureted 4-stroke engines. Not all "equivalent" plugs are 100% identical in heat range.

 

[corey61]

"A quarter of a step off" ways my way of saying that I've seen plugs which were listed as cross-overs for each other run at different temperatures in practice. This was common during my 2-stroke bike days, but I've also seen it with carbureted 4-stroke engines. Not all "equivalent" plugs are 100% identical in heat range.

Interesting. So, how would you think those differences in heat range for the Bosch and NGK plugs would affect performance, in our Flying Brick engines? Given your sense of the NGK plugs being 'a quarter step off' the Bosch plugs, which would give better performance, i.e, ability to deliver strong, repeatable spark, under heavy load or sustained high-RPM operation? From the way you said it, I took it to mean that the Bosch plugs were slightly better. But it might be hard to generalize about this... and maybe we're getting off into the weeds here!

 

[corey61]

I think it's a bit sleazy for a vendor to say that a product is discontinued by the manufacturer (mentally pushing customers to seek an alternative) if in reality it's only unavailable from that vendor. BBY did not try to tell us that Brembo products had been discontinued by Brembo when in fact Brembo had only stopped selling to BBY. Of course, BBY didn't have an alternative to sell so there was no motivation to say that.

I will ask my dealership next week if they know anything about a discontinuation of the XR7LDC plug.

Well, it does seem that the Bosch XR7LDC has indeed been discontinued, and it's not just a matter of euromotoelectrics not being able to get them.

https://www.boschsparkplugs.net/bosch-xr7ldc-0242135500770-nickel-spark-plug


BTW, you and I chatted in this forum about these plugs when I changed them three years ago!

https://forums.bmwmoa.org/showthread.php?96037-Bosch-XR7LDC-spark-plugs-different-flavors

 

[drneo66]

Interesting. So, how would you think those differences in heat range for the Bosch and NGK plugs would affect performance, in our Flying Brick engines? Given your sense of the NGK plugs being 'a quarter step off' the Bosch plugs, which would give better performance, i.e, ability to deliver strong, repeatable spark, under heavy load or sustained high-RPM operation? From the way you said it, I took it to mean that the Bosch plugs were slightly better. But it might be hard to generalize about this... and maybe we're getting off into the weeds here!

The problem is that we are guessing here about these specific plugs. I'm sure with some research you can find the published heat ranges of the NGK and Bosch. Since this is the internet, I'm betting we can find someone who's motor blew up with fresh Bosch plugs and some guy whose engine has gone 250k miles with NGK plugs and haven't missed a beat. Sorry, I'm not trying to dismiss Mr. Feeler's past experiences.

Also, do you think each same model of the same plug runs at exactly the same temperature setpoint? I have no idea what the tolerance level for these are...

I think you're way in the weeds here (been there myself quite a few times), especially because there's going to be a number of people who are going to buy the NGK plugs (or have them installed at the dealer) without sitting on a forum for 3 days researching the difference.