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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
Vice President, Vintage BMW Motorcycle Owners
2022 BMW Friend Of the Marque
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 B9HS-10 (3626), my first choice, has been superseded to a resistor plug, BR9HS-10 (4551).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 NGK B8HS (5510), which would have been my second choice, has been superseded to resistor version BR8HS (4322).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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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
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2022 BMW Friend Of the Marque
Long Island, New York

xackley
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Re: A question about spark plugs

Post by xackley »

The other day when I had a carb problem, I tried to buy a couple B8hs for my R69. With my location I have the options of NAPA and AdvanceAuto.
NAPA only had b7hs, Advance had nothing that was not resistance.

Yesterday I order 4 b8hs from NAPA, which should be a life time supply for me.

When I bumped the order, the web site said there were only 5 available!

Luckily, when running right the plugs seem to last forever, so maybe the plugs will last until finding gasoline becomes the problem.

Don
1958 R69, 1972 R75/5, 1980 XS650, 1982 GL1100, 2003 guzzi ev, 2017 guzzi V7!!!
All on the road, going no where in particular in the Finger Lakes of New York

Bolti
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Re: A question about spark plugs

Post by Bolti »

So chaps hello from the UK.
The question of spark plugs…….
I have a R69S and have just converted the bike over to a Vape electronic ignition system which has eliminated differential timing and bad starting.
My thoughts were to change the plugs over now that I have updated the ignition system to Iridium spark plugs.
Has anybody got a comment or experience of fitting and electronic ignition and iridium spark plugs out there and what are their conclusions.
Thanks chaps

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jwonder
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Re: A question about spark plugs

Post by jwonder »

I too had the Vape installed on my R 69 S. The question was more around the total resistance to the plug. The Vape manual suggests:
Do not use spark plug sockets with a resistance of more than 5kOhm. Better use 1 or 2kOhm
ones. Bear in mind that spark plug sockets do age and thereby increase their internal
resistance. Should an engine start up only when cold, a defective spark plug socket and/or
spark plug is very probably the cause. In case of problems check high tension cables too.
After looking around it seems as if most plugs are in the 5kOhm range themselves. Meaning if you have a 5kOhm plug you would need a 0kOhm socket to meet the Vape maximum specifications. The main reason for running iridium plugs in cars is to increase the life of the plug and decrease service intervals. We do not have those issues in our vintage BMW's and honestly with the "sprinkler system" Bing carbs I do not see the extra cost as being justified.

-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-

On a 100% different note and a small warning:

First off, I love the Vape ignition system, I have it on many of my motorcycles!

That being said, I needed to remove the Vape ignition from my 1967 R 69 S due to the fact that the factory started to lighten the flywheels sometime after 1965. With the increased compression of the R 69 S and the light flywheel the motorcycle would start perfectly when cold, but would NOT start when hot. I tried several different coils from Vape and purchased a whole new system to debug the problem. Nothing helped. The Vape system needs two full rotations for the computer to know where to fire the plug and when hot I very rarely could generate two full rotations. I figured out how to start it hot, but it was quite hard and would take 10-30 kicks even knowing the way to get it started when hot. I decided to leave the 12 volt alternator in and put the original ignition back in and its very happy both hot and cold. 1 kick anytime!

I hope these items help!
James Wonder
Vice President, Vintage BMW Motorcycle Owners
2022 BMW Friend Of the Marque
Long Island, New York

Daves79x
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Re: A question about spark plugs

Post by Daves79x »

That's a great point James! Guys have had a lot of trouble starting bikes with these systems and lightened flywheels. You've put a lot of work into proving it.

Dave
Dave

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