A question about spark plugs

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jwonder
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Re: A question about spark plugs

Post by jwonder »

wa1nca wrote:
Mon May 31, 2021 1:43 pm
James
the -10 after B9HS-10 denotes the factory plug gap for the plug with higher numbers being larger gaps.

Does that mean the factory spec for this plug gap is 1.0 mm or 0.03937008" or .040"
Tommy
Great question tommy. There is a “standard” gap per plug type. Who knows who came up with it I don’t know. It differs based on the type. Ngk uses the -10, -20 and -30 designation for wider gaps.

It really does not matter as long as it’s not an iridium plug. Never gap an iridium plug as you break the iridium off the tip.
James Wonder
Long Island, New York

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miller6997
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Re: A question about spark plugs

Post by miller6997 »

In searching for a suitable plug for my R69S with R69 pistons, here is what I learned from NGK:

1. B9HS-10 (3626), my first choice, has been superseded to a resistor plug, BR9HS-10 (4551). The non-resistor 3626 is still around but not easy to find. I ordered a set from Harvard Marine through Amazon, but they never arrived and the seller never responded, so I canceled the order and am waiting for a refund.
:x Footnote: The Harvard Marine shipment finally arrived and it contained the 4551 resistor plugs, not the 3626 B9HS version. When I told the company's customer rep that I had received the wrong plugs, he basically told me to f---off, but I did get a refund and was told to keep the incorrect plugs. :x

2. NGK B8HS (5510), which would have been my second choice, has been superseded to resistor version BR8HS (4322). The 5510 non-resistor version is still around but it is not easily available.

3. NGK B8HS-10 (5126) comes out of the box gapped at .040. To my surprise, NGK tech support advises that "the maximum you can move the ground electrode is .012 +/-. anything beyond that can compromise the weld and can cause the ground to break off." I need a gap of .024, achieving which would exceed that maximum tweak. It would probably be OK, but I would not like to be a test case.

As suggested here in this discussion, I also considered the Champion L77JC4 but discovered that it will not work with the brown BMW plug caps, which require a threaded post.

Finally, I called Vech (which, of course, is what I should have done at the beginning) and he is now recommending the Beru version 114Z-4au. I ordered four of these from him and am looking forward to the delivery.
Jon Miller
'67 R69S
'13 F800GT
Altadena, California

chrishea
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Re: A question about spark plugs

Post by chrishea »

Years ago the local "mom and pop" dealer, Tacoma BMW, would sell ND (now Denso) spark plugs. That's what they carried and they worked fine in my post 1970 Airheads. When the dealer got bought out, I switched to NGKs as the new guys sold the BMW branded Bosch plugs for a song, when NGK stopped non-resistor plugs I went back to the Densos - today I had some time and I looked up the cross reference for the Slash-2: R60 short reach should be W24FS-U, stock number 4038; R69 short reach W27FS-U, stock number 4052; R60 long reach W24ES-U, stock number 4030; R69 long reach W27ES-U stock number 4046. You might want to double check. I haven't used those myself, I still have a few NGKs left for my LK 1966 R60. The NDs are coated like the Bosch plugs used to be, more of a chrome finish, I find the zinc coated NGKs rust. FYI for later Airheads - W5DC is a W22EP-U and W7DC is a W20EP-U. There isn't a direct translation to W6DC, the tables show the W20EP-U, however, I use the W22EP-U for my W6DC applications.
I've been buying Densos in bulk from RockAuto when I buy car parts, they are about $2 per plug! Watch RockAuto though - they can get you on the "shipping from multiple warehouses" with some high shipping fees. I bundle when I buy parts for my 4-wheelers.
Chris
Seattle

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waldoverkill
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Re: A question about spark plugs

Post by waldoverkill »

miller6997 wrote:
Mon Jun 14, 2021 3:52 pm


As suggested here in this discussion, I also considered the Champion L77JC4 but discovered that it will not work with the brown BMW plug caps, which require a threaded post.
I had the threaded post issue when I purchased plugs and thought I had messed up. Then I found that you can unscrew the end of the sparkplug and underneath is a nice thread that fits the brown caps.

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miller6997
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Re: A question about spark plugs

Post by miller6997 »

On most spark plugs, and certainly on the NGK, Beru, and Bosch versions, that metal tip simply screws off and reveals the threaded post underneath. The Champions are different. The metal tip requires some effort to take it off, and when you do that, you'll find that it has an embedded screw in it that screws into the porcelain of the Champion plug. When the tip is removed, it leaves just a hole in the porcelain of the plug where it used to be, and there is nothing for the brown BMW cap to attach to.
Jon Miller
'67 R69S
'13 F800GT
Altadena, California

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jwonder
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Re: A question about spark plugs

Post by jwonder »

miller6997 wrote:
Mon Jun 14, 2021 3:52 pm
As suggested here in this discussion, I also considered the Champion L77JC4 but discovered that it will not work with the brown BMW plug caps, which require a threaded post.
Jon, apologies! The website I was looking at said those had removable tops. After looking at pictures of the ones available online, they do not!

I changed my original post to not confuse anyone!
James Wonder
Long Island, New York

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