SPARK PLUGS FOR 650 CSR

Information relating to the Matchless G12 or AJS Model 31 650cc twin
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SPARK PLUGS FOR 650 CSR

Postby JEAN-NOEL » Thu Dec 19, 2019 10:12 am

Hello Gents,
I realize that I don't have spare spark plugs. According to my owner's manual the right model is KLG FE 220. MATCHLESS CLUELESS states as modern equivalent NGK B9ES, or CHAMPION N2C.
But AMOC PARTS SERVICE offers N3C for 650 CRS or N4C for 650 STD 1964 - on plus CSR...
I have found NGK B9ES for only £ 1.74 each.
I am now confused, because I don't know which is the best model that I can use, avoiding of course counterfeits. Obviously N2C, N3C, N4C haven't the same thermical indice.
Has anyone an opinion on the subject ?
Your advices welcome !
Kind regards.

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Re: SPARK PLUGS FOR 650 CSR

Postby Eamonn » Thu Dec 19, 2019 1:54 pm

Take a look at this posting from Rob:

viewtopic.php?f=11&t=21184&start=50


At the end of the discussion there is a PDF file that contains the results of asking the Forum members what plugs they use. It may be of help....

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Re: SPARK PLUGS FOR 650 CSR

Postby clive » Fri Dec 20, 2019 11:50 am

Personally my experience with a 500 single with magneto is that it will not run properly for long on an NGK plug. Others I know have the same experience. I always go for Champion. May not be a problem with coil ignition
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Re: SPARK PLUGS FOR 650 CSR

Postby SPRIDDLER » Fri Dec 20, 2019 12:05 pm

clive wrote:Personally my experience with a 500 single with magneto is that it will not run properly for long on an NGK plug. Others I know have the same experience. I always go for Champion. May not be a problem with coil ignition

My one previous owner '46 500 (magneto) that had been in store for 26 years was a right devil to start and didn't run well on a new NGK either. It was happiest with the ancient Lodge FE80 that was already fitted when I got it.
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Re: SPARK PLUGS FOR 650 CSR

Postby Reynard24 » Fri Dec 20, 2019 12:38 pm

I run all my bikes on NGK plugs and have never had a problem with them whether they are magneto or coil ignition. In fact I haven't had to change a plug for years, similarly I leave my bikes over winter and have never had issues with bad starting due to stale petrol. I don't own a 650CSR but my G12DL (magneto) runs very well with B7ES plugs.
Maybe I'm just very lucky?

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Re: SPARK PLUGS FOR 650 CSR

Postby MalcW » Fri Dec 20, 2019 12:41 pm

clive wrote:Personally my experience with a 500 single with magneto is that it will not run properly for long on an NGK plug. Others I know have the same experience. I always go for Champion. May not be a problem with coil ignition


Ditto with my magneto equipped Model 31 D/L. I now use Champion N5Cs, which (touch wood) are working well.

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Re: SPARK PLUGS FOR 650 CSR

Postby SPRIDDLER » Fri Dec 20, 2019 1:13 pm

I've never had any but there are said to be some fake NGK's circulating - mainly on auction sites and at jumbles.
NGK fake plugs (640x398).jpg
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Re: SPARK PLUGS FOR 650 CSR

Postby JEAN-NOEL » Sat Dec 21, 2019 11:02 am

Thank you all for your skilled advices ! I realize I had missed the excellent Mr HARKNETT job's...Very interesting. So Spriddler's post regarding counterfeits.
Just checked what are my sparking plugs : N3C, very prone to fouling on the left cylinder and both are sooty.
I have inverted the plugs to see : there is always a problem on the left side. The mag has been fully refurbished.
I will try N4C or B7ES to see if there is an improvement. And I will investigate around the carb to lean the mixture.
My engine is not yet runned in, and I don't exceed 3000 RPM and max 1/3 throttle, so it is difficult to deal with the main jet or the needle. My carb is correctly setted according the manual : n° 4 slide, 4th notch, 450 main, 20 pilot, 0.106
It is also interesting to know that some users fit hotter N5C on their CSR with no problems.
Kind regards. J.N.

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Re: SPARK PLUGS FOR 650 CSR

Postby petert120r » Sun Dec 22, 2019 11:32 am

There was some correspondence recently in one of the classic bike mags about the limited lifespan and fouling of modern plugs in old engines. The suggestion was to use "Brisk" plugs which apparently mitigate some of these problems. Available from F2 Motorcycles - see their website for details and explanations.

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Re: SPARK PLUGS FOR 650 CSR

Postby bob121 » Thu Dec 26, 2019 2:31 pm

Champion n5c in mine. They have done a few thousand miles now (also use higher octane fuel) . The ngks only lasted a few hundred miles. Makes no sense and shouldn't make any difference.

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