Best spark plug?

[gatorvetnm]

Hello!
I am replacing the spark plugs on my 1974 R90/6 for the first time. It came with Bosch spark plugs that say "Super 942" and on the barrel is stamped W6DC Germany.
I just can't find them anywhere. Have they been discontinued? What's my best option?
Thanks so much,
Danny

 

[20774]

Welcome to the forum! Check out Snowbum's page on spark plugs. I thought NAPA might be selling something similar to Bosch but with a different number...not so sure. But NGK seems to be a good choice:

SPARK PLUGS, spark plug caps, antiseize compound, BMW motorcycles

spark plugs, spark plug caps, antiseize, BMW Airhead and Classic K-bike motorcycles

bmwmotorcycletech.info

 

[52184]

Hello!
I am replacing the spark plugs on my 1974 R90/6 for the first time. It came with Bosch spark plugs that say "Super 942" and on the barrel is stamped W6DC Germany.
I just can't find them anywhere. Have they been discontinued? What's my best option?
Thanks so much,
Danny

Nippon Denso W20EPU.

The Bosch plug you removed is a non-resistor plug, exactly what you want for your ignition system. The Bosch non-resistor plugs are NLA through legitimate channels (lots of forgeries out there). We used to use NGK BP6ES but those are NLA also, having been replaced by the BPR6ES which is a resistor plug. And NGK has also been subject to forgeries popping up on places like Amazon or fleabay, so be leery of any sites offering the BP6ES plugs online. The ND W20EPU is widely available at reputable vendors like NAPA or…MaxBMW.com

Best,
DeVern

 

[88bmwjeff]

Nippon Denso W20EPU.

We used to use NGK BP6ES but those are NLA also, having been replaced by the BPR6ES which is a resistor plug. And NGK has also been subject to forgeries popping up on places like Amazon or fleabay, so be leery of any sites offering the BP6ES plugs online. The ND W20EPU is widely available at reputable vendors like NAPA or…MaxBMW.com

Best,
DeVern

Euro Motoelectrics has the BP6ES in stock and available.

NGK - Center Electrode NON Resistor Spark Plug - BMW R Airhead ; BP6ES / NGK

Part #:: BP6ES NGK Single Electrode NON Resistor Spark Plug. NGK Equivalent to the Bosch W6DC, WR6DCPLUS, W7DC, and WR7DCPLUS spark plugs. Vehicle Manufacturer: BMW Application: AIRHEADS; ALL

www.euromotoelectrics.com

 

[melville]

I've had no problem getting W6DC (and W5DC-colder, and W7DC-warmer) Bosch plugs from my local ACVW shop. Airheads take the same thread and reach spec as a Type 4 VW. One of my bikes is dual-plugged and uses Type 1 spec plugs in the lower hole and again W5, W6, and W7 are readily available.

 

[gatorvetnm]

Nippon Denso W20EPU.

The Bosch plug you removed is a non-resistor plug, exactly what you want for your ignition system. The Bosch non-resistor plugs are NLA through legitimate channels (lots of forgeries out there). We used to use NGK BP6ES but those are NLA also, having been replaced by the BPR6ES which is a resistor plug. And NGK has also been subject to forgeries popping up on places like Amazon or fleabay, so be leery of any sites offering the BP6ES plugs online. The ND W20EPU is widely available at reputable vendors like NAPA or…MaxBMW.com

Best,
DeVern

Thanks so much!

 

[52184]

You are welcome!

Note that you also have the option, down the road, of changing out your plug wires and caps to non-resistor and switching to the more commonly available resistor plugs. That gives you the same desired effect of having 5k ohm resistance on each cylinder. And, I should have noted that you may still be able to get the Bosch or NGK plugs I referred to in some distribution channels, as when their discontinuance was announced some time ago some channels stocked up, anticipating a lengthy changeover process. In fact, according to the parts fiche, you can still buy the W6DC plugs from your friendly local BMW dealer-- part# 12 12 1 338 145 at only $9.18 each. Whether that’s because BMW stocked up large, or has a proprietary distribution agreement with Bosch, is speculative—tho I note that some of the long-time BMW aftermarket parts sources are no longer able to sell things like brake caliper or master cylinder rebuild kits due to them being distribution-limited. And BMW is certainly within their right to contract with a supplier to produce X number of widgets to Y specification and distribute them solely in the BMW channel—at least under the current “right to repair” status here in the US. Those of us who do most of our own repair work have been able to get around some of the brake part issues thanks to sources like Bevel Heaven. And, I should note that regardless of what parts a vendor still has listed in their online store, they aren’t available until the parts are delivered and verified as genuine. But, I digress...

The resistor plug issue was a long discussion a couple of years ago on the Airheads list. Resistor plugs were developed decades ago, partly to resolve RF interference issues--first with radios then with engine electronics. Developments and improvements in vehicle electronics and shielding progressed and newer vehicles began using resistor plugs instead of resistor caps/wires for a lot of reasons—the resistance value is refreshed each time the plug is renewed, cables and caps can all be standardized as non-resistor, etc. That simplifies everything from manufacturing to parts inventory and availability to repair, as well as eliminating confusion over where the desired resistance will be introduced to the system. It is what it is, and as more manufacturers drop production of non-resistor plugs old standbys like the W6DC and BP6ES more and more become niche products and not profitable for their manufacturers or distribution channels. If you can find them somewhere in the distribution channel now and can verify their authenticity, stock up—I did a couple years ago.

On the Bosch W6DC, checking at BoschSparkplugs.net (a Bosch distributor) yields thus: https://www.boschsparkplugs.net/search/all?pn=W6DC .
That link shows the W6DC (Bosch part# 7594) along with a link to Details, and clicking the Details link pulls up the following: https://www.boschsparkplugs.net/bosch-7594-w6dc-super-spark-plug ,which shows the plug as discontinued.

For NGK BP6ES plugs (#7333) the situation is the same. Searching for that part on ngksparkplugs.com comes up empty (https://ngksparkplugs.com/en/part-finder) and searching by vehicle on that site, for an airhead, pulls up a recommendation for the BPR6ES (#7131) or an Iridium plug that is also a resistor plug. Jumping over to NGK.com and searching for the BP6ES yields the same result: https://www.ngk.com/search/all?q=BP6ES and following the Details link there also shows the plug as discontinued https://www.ngk.com/ngk-7333-bp6es-nickel-spark-plug and the recommendation for the BPR6ES as the replacement.

So, it’s a case of “smoke em if you’ve got ‘em”, or more correctly, “buy ‘em if you find ‘em” and can verify they are genuine. Lots of fakes out there, I myself got a bad set of 8 from Amazon a couple of years ago—but they were quickly refunded. And FleaBay is even worse, I suspect. For now, I have a stash of my own NGK but I keep the Denso plugs on hand for Tech Days and for my own use, and they have performed well and are still readily available. For now.

Sorry to be so long-winded but wanted to lay it all out,

DeVern

 

[88bmwjeff]

The resistor plug issue was a long discussion a couple of years ago on the Airheads list. Resistor plugs were developed decades ago, partly to resolve RF interference issues--first with radios then with engine electronics. Developments and improvements in vehicle electronics and shielding progressed and newer vehicles began using resistor plugs instead of resistor caps/wires for a lot of reasons—the resistance value is refreshed each time the plug is renewed, cables and caps can all be standardized as non-resistor, etc. That simplifies everything from manufacturing to parts inventory and availability to repair, as well as eliminating confusion over where the desired resistance will be introduced to the system. It is what it is, and as more manufacturers drop production of non-resistor plugs old standbys like the W6DC and BP6ES more and more become niche products and not profitable for their manufacturers or distribution channels. If you can find them somewhere in the distribution channel now and can verify their authenticity, stock up—I did a couple years ago.

DeVern

Here's an odd point. I certainly am not knowledgeable in this area, but my curiosity has me wondering why one can't use resistor plugs and non-resistor caps/wires? Of course, this would only seem to work if the total resistance of the cap, wires and plug were the same for both configurations.

On a side note, time to order a bunch of plugs from EME.

 

[52184]

Here's an odd point. I certainly am not knowledgeable in this area, but my curiosity has me wondering why one can't use resistor plugs and non-resistor caps/wires? Of course, this would only seem to work if the total resistance of the cap, wires and plug were the same for both configurations.

On a side note, time to order a bunch of plugs from EME.

You can, as noted in the paragraph above the one quoted. As long as both cylinders have 5k ohms resistance, via either plug or plug cap, your airhead ignition system will be happy. It’s when that resistance drops to zero or rises to 10k ohms per side that problems can arise.
Best,
DeVern

 

[88bmwjeff]

DeVern,
Thanks. Missed that point earlier.

 

[pmcmahon]

How does one identify the fakes? Are the visually different or is it in the performance? A few years back I bought a box I believe from Amazon, I’ll have to give them a second look.

 

[Omega Man]

How does one identify the fakes? Are the visually different or is it in the performance? A few years back I bought a box I believe from Amazon, I’ll have to give them a second look.

A bit of recent discussion on genuine/fake plugs here-

NGK LMAR8D-J Spark Plugs

I just bought a set of these NGK LMAR8D-J spark plugs from a local motorcycle accessories dealer, not Amazon. And having seen a couple of YouTube videos about "fake" NGK spark plugs, I had a close look at the ones I bought. They appeared to be genuine but when doing a resistance measurement of...

forums.bmwmoa.org

OM

 

[lkchris]

Nippon Denso W20EPU.

The Bosch plug you removed is a non-resistor plug, exactly what you want for your ignition system. The Bosch non-resistor plugs are NLA through legitimate channels (lots of forgeries out there). We used to use NGK BP6ES but those are NLA also, having been replaced by the BPR6ES which is a resistor plug. And NGK has also been subject to forgeries popping up on places like Amazon or fleabay, so be leery of any sites offering the BP6ES plugs online. The ND W20EPU is widely available at reputable vendors like NAPA or…MaxBMW.com

Best,
DeVern

I would check with a BMW dealer.

The thing is, Bosch USA is essentially a separate company from Bosch Germany and somehow believes all spark plugs should be resistor plugs. They do not necessarily source the things they sell from Bosch Germany. This is a problem for my Mercedes, too. The dealer parts system sources parts from Germany.

I would caution my statement in that I haven't owned an Airhead for 10 years or so now and haven't shopped for plugs since. Things could be different than they were 10 years ago. In any event, you will not be financially ruined giving some business to a dealer and it's always good to know the folks there.

Another "the thing is" ... Airheads are now vintage motorcycles ... you cannot source proper tube type tires for Airheads in the USA either and if that's what you want, you'll have to purchase them from European sources where they are still available. If you want tires for your 1970s Mercedes, you'll probably need to shop Coker Tire.

The world has moved on from 1970s vehicles and, again, you are an "enthusiast" with a vintage vehicle.

 

[pglaves]

I would check with a BMW dealer.

I would caution my statement in that I haven't owned an Airhead for 10 years or so now and haven't shopped for plugs since. Things could be different than they were 10 years ago. In any event, you will not be financially ruined giving some business to a dealer and it's always good to know the folks there.

Too many dealers won't work on Airhead motorcycles. Many, not any motorcycle over 10 years old. This is almost certainly true of the too-many huge multi-brand dealers.

When they won't work on vehicles I don't necessarily trust their decisions about parts for those vehicles; especially parts not specifically BMW OEM parts.