Author Topic: Spark plugs for the A7SS  (Read 1385 times)

Offline BSA500

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Spark plugs for the A7SS
« on: 21.03. 2016 13:01 »
Hi,
Again after a long lay up(replacing crankshaft shims) one of the NGK plugs has died. So I am looking for other suppliers/manufacturers of plugs to try. I have used Champs in the past but have heard bosch ones are great. What would be the direct replacement of the bosch's or other makes be please.
Andy

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Re: Spark plugs for the A7SS
« Reply #1 on: 21.03. 2016 14:44 »
G'day BSA500.
I use NGK B7ES, lots of equivalents http://www.sparkplug-crossreference.com/convert/NGK_PN/B7ES
With unleaded they might read rich in which case I'd use B6ES.
Cheers
'51 A7 plunger, '57 A7SS now A10CR,  '83 CB1100F, .
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Offline BSA500

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Re: Spark plugs for the A7SS
« Reply #2 on: 21.03. 2016 15:11 »
Yeah I have tried both those grades and the NGK with the extended nose? to burn better?. But all cases they fail without any reason it seems. The burn is a nice brown tip so I think I need to try another type.

Offline BSA500

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Re: Spark plugs for the A7SS
« Reply #3 on: 22.03. 2016 09:01 »
I have ordered a pair of Bosch WC33 so I will see how that goes

Online BSA_54A10

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Re: Spark plugs for the A7SS
« Reply #4 on: 22.03. 2016 11:19 »
If you are getting a good burn I will guess that you are blaming the wrong party.
If you find the plugs are going "bad" when you try to start the bike from cold, then it is your fuel and not the plugs that needs changing.
I have found that if the bike is likely to be cold when I start it the I need to starve the engine rather than turn it off.
If it is a short stop say for fuel and the bike will be hot when I try & restart then I can turn the engine off normally.

The reason is that modern fuels have oily parts that are very conductive at cylinder pressures and these drop out of solution as the pressure increases.
This is exactly the same mechanism as water condensing in your air compressor.
These conductive fractions deposit on the spark plug and make it go wet short so it will spark happliy out side the cylinder but track down the side of the insulator inside the engine.
Bike Beesa
Trevor

Offline BSA500

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Re: Spark plugs for the A7SS
« Reply #5 on: 22.03. 2016 16:21 »
Over the years I have had plug failures at all sorts of times engine hot/cold and once running full pelt. The most common factors are 1.NGK and 2. worse over the last few years. Which could either be changes in fuel or plug materials/manufacture or a combination of both. I using this BSA for 25+ years and in the beginning NGK was always the first choice, not now. (I have also had some issues with Champions over the years). So we shall see how the Bosch fares.

Offline roadrocket.chris

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Re: Spark plugs for the A7SS
« Reply #6 on: 03.04. 2016 16:49 »
i had problems with ngk and champions in my twin carb rocket then a friend gave two ngk iridium plugs what a difference sparks like lighting bolts starts second kick and ticks over like a clock, ive yet to see how long they will last bui i am very impressed....
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Offline Rocket Racer

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Re: Spark plugs for the A7SS
« Reply #7 on: 04.04. 2016 09:14 »
I had a number of issues with NGK plugs and apparently the ceramic glazing is porous these days so they foul more readily.
I run fancy NGK's on my race a10 and budget champions in my road engines.
A good rider periodically checks all nuts and bolts with a spanner to see that they are tight - Instruction Manual for BSA B series, p46, para 2.
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Re: Spark plugs for the A7SS
« Reply #8 on: 04.04. 2016 14:02 »
Well actually the problem is the porceain insulaor is not glazed.
Problem is that the only glaze that will withstand the higher temperatures of modern lean burn fuels is lead based.
And as any one who never did either physics nor chemistry will know you can not use a lead based glaze in a spark plug or you will kill off all life on the planet.
Bike Beesa
Trevor

Offline BSA500

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Re: Spark plugs for the A7SS
« Reply #9 on: 17.05. 2016 18:00 »
Ok tried the Bosch plugs and again one failed after about 50 miles. Backfiring etc then nothing. Pulled the plug and wet with petrol. I am thinking of changing the pilot jet down from 30 to 25 as she puffs black smoke with a little rev at standstill. Carb has been resleeved and is running a new needle and jet. I cannot believe the fault lies with the mag or all those previous plugs.

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Re: Spark plugs for the A7SS
« Reply #10 on: 17.05. 2016 20:44 »
G'day BSA500.
Your on the right track. Too rich a pilot or float height will give that symptom.
Cheers
'51 A7 plunger, '57 A7SS now A10CR,  '83 CB1100F, .
Australia
Muskys Plunger A7

Offline BSA500

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Re: Spark plugs for the A7SS
« Reply #11 on: 17.05. 2016 20:54 »
Yep the spec for the A7SS has always said 30 pilot but with the carb being @new@ and the problem still there its worth a try

Offline KeithJ

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Re: Spark plugs for the A7SS
« Reply #12 on: 19.05. 2016 09:59 »
Well actually the problem is the porceain insulaor is not glazed.
Problem is that the only glaze that will withstand the higher temperatures of modern lean burn fuels is lead based.
And as any one who never did either physics nor chemistry will know you can not use a lead based glaze in a spark plug or you will kill off all life on the planet.


I had heard NGK pugs used to be glazed but now aren't.  I asked technical guy at one of the exhibitions and he said they had never been glazed!  So not sure what the issue is.  Not had this on my A10 but certainly and issue on another bike.  From what has been posted, fuel could well be the issue.
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Offline rocker21

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Re: Spark plugs for the A7SS
« Reply #13 on: 14.07. 2016 15:09 »
modern Ethernol based fuels do burn differently and do eat plugs and other things, in the UK go to Tesco and use their 99 octane unleaded fuel, runs really well, i use NGK BP7EV or BP7EVX plugs think they have recently replaced with a different no, I have a 1960 A7ss .
there is another petrol you can buy that does not have all this rubbish in it, made in Sweden , not cheap but works fine and no need to drain the fuel tank or anything else, does not go off like modern fuel, it is just Petrol and nothing else.
 

Offline a101960

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Re: Spark plugs for the A7SS
« Reply #14 on: 14.07. 2016 19:37 »
Quote
in the UK go to Tesco and use their 99 octane unleaded fuel, runs really well,
Yeah, my RGS loves it, it is the best petrol that I have found.