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A question about spark plugs

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miller6997
Posts: 1182
Joined: Fri Oct 27, 2006 3:00 am

A question about spark plugs

Post by miller6997 »

Several years ago, Vech recommended NGK B9HS-10 (3626) spark plugs for the R69S. NGK has discontinued this plug and now advises replacement with B9HS-10 (4551). I'm about to place an order and wonder, what plugs do others on the list use?

On a related topic, Vech also argues that, once flooded, a spark plug should be replaced, not dried and reused. I'm sure that most of us have had this flooding happen, probably more than once. Do you scrap a plug after the first incident?
Jon Miller
'67 R69S
'13 F800GT
Altadena, California

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schrader7032
Posts: 8286
Joined: Fri Oct 27, 2006 3:00 am
Location: San Antonio, TX

Re: A question about spark plugs

Post by schrader7032 »

I bought Bosch plugs from Vech many years ago...still in the bike. They are W3CC and I believe the updated Bosch number is 7529. My heads are LK or long reach. I've heard Vech say once a plug is fouled with gas, it should be replaced. I've flooded my engine a number of times and have never bothered to replace the plugs. Sometimes I might have to take them out of the engine to more quickly dry/air them out, but I can't see replacing a plug for this reason.

In the NGK number B9HS, does the H stand for short reach, eg 1/2"? I did a search for NGK 3626 and got some hits on Amazon and it said they were not discontinued. What's the difference a 3626 and 4551 plug? Still a B9HS-10 plug, right?
Kurt in S.A.
'78 R100/7 '69 R69S '52 R25/2
Fast. Neat. Average. Friendly. Good. Good.

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wa1nca
Posts: 1005
Joined: Thu Sep 27, 2012 5:15 pm
Location: Ashfield Ma

Re: A question about spark plugs

Post by wa1nca »

NGK
H is 1/2 inch
E is 3/4 inch
Tommy Byrnes
54 R51/3 55 R50/Velorex 560 sidecar 64 R27 68 R69US 75 R75/6
Ashfield, Ma
USA

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jwonder
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Re: A question about spark plugs

Post by jwonder »

Hello, I figured I would weigh in here as well.

First off, the problem is that most of the companies have stopped making non-resistor spark plugs. They are rapidly becoming hard to find and the powersports/racing crowd still use them to some degree and they are re-marketing them at 3 times the price.

You do not want to use a resistor plug if at all possible. The standard is 5k resistance and if you are running the 1k plug caps that means 6k total which is a lot for the magneto ignition.

By the way, the -10 after B9HS-10 denotes the factory plug gap for the plug with higher numbers being larger gaps.

The standard for the R50/2 and R60/2 is B8HS, and the R69S people like to run the colder B9HS. Honestly I do not feel the colder plug is that required and if someone wants to disagree I would like to hear why. If you are riding it like you're on a race track the colder plug will help with the higher compression, but on the road I am not so sure. If you look at the cross-reference for both the B9HS and B8HS, many times they cross to the same plugs as they are very close in heat range.

So, what are the options available today (and again if someone has a plug they are using that works, please post it):

1/2" reach: Autolite 4092 (it crosses to both B8 and B9) (Ignore my suggestion of the L77JC4 please)
3/4" reach: Denso 4046 W27ES-U

I also found the B9ES, B8HS and B9HS available at: https://www.sip-scootershop.com/en/prod ... er_NGKB9ES over in the UK if you want to pay for shipping.

I hope this helps.

James
James Wonder
Vice President, Vintage BMW Motorcycle Owners
Long Island, New York

sorbo1
Posts: 41
Joined: Fri May 16, 2014 6:45 pm

Re: A question about spark plugs

Post by sorbo1 »

Hi
My 2 cents worth , I have a 1961 R69s with R69 lower compression pistons . I have been using NGK B 6HS plugs for the last 2 or 3 years with out any problems . These are short reach plugs . The bike is used on a freeway at speeds up to 100 Kilometers per hour or 60 MPH . The bike start first or second kick . I have had the odd time when I have flooded the bike but have always still kept using the same plugs .
Hope this is of some help .

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miller6997
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Joined: Fri Oct 27, 2006 3:00 am

Re: A question about spark plugs

Post by miller6997 »

It is the NGK website that lists the B9HS(3626) plug as discontinued. They are still available in several places, including Amazon and eBay, with prices that are all over the place. I'll have the replacement 4551 tomorrow and will report on how it works out.
Jon Miller
'67 R69S
'13 F800GT
Altadena, California

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Micha
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Location: Israel

Re: A question about spark plugs

Post by Micha »

Never heard before, that a wet plug should not be used again :shock:
What's the reason?
Michael Steinmann
R51/3 1952
Engine Nr. 529466

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wa1nca
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Joined: Thu Sep 27, 2012 5:15 pm
Location: Ashfield Ma

Re: A question about spark plugs

Post by wa1nca »

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
Last edited by wa1nca on Mon May 31, 2021 2:03 pm, edited 2 times in total.
Tommy Byrnes
54 R51/3 55 R50/Velorex 560 sidecar 64 R27 68 R69US 75 R75/6
Ashfield, Ma
USA

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wa1nca
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Joined: Thu Sep 27, 2012 5:15 pm
Location: Ashfield Ma

Re: A question about spark plugs

Post by wa1nca »

Micha wrote:
Mon May 31, 2021 1:28 pm
Never heard before, that a wet plug should not be used again :shock:
What's the reason?
Good question
Vech also told me this
I dont know
Tommy Byrnes
54 R51/3 55 R50/Velorex 560 sidecar 64 R27 68 R69US 75 R75/6
Ashfield, Ma
USA

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miller6997
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Joined: Fri Oct 27, 2006 3:00 am

Re: A question about spark plugs

Post by miller6997 »

Sorry, I’ve caused some confusion.

Looking for information on NGK plugs, I went to ngk.com, and there I read that the B9HS-10 (3626) was discontinued, with the recommendation of part number 4551 as an alternative. Relying on that advice, I ordered and received two of those from Amazon and when they arrived I realized that I had made two mistakes.

First, the 4551 plug is a BR9HS-10. Note the R. That is a resistor plug. It is not a straight replacement for the 3626.

Second, ngk.com is NOT the website for the NGK company. I missed the fine-print disclaimer on the very top of their home page. The correct URL for NGK is ngksparkplugs.com, where the information is no doubt more reliable.

Starting over, I have ordered two B9HS-10 (3626) plugs, and until they arrive, I am going to the woodshed.
Jon Miller
'67 R69S
'13 F800GT
Altadena, California

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