The BSA A7-A10 Forum
Technical (Descriptive Topic Titles - Stay on Topic) => Lucas, Ignition, Charging, Electrical => Topic started by: michaelfish on 25.03. 2009 17:37
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I have owned my 1960 a10 Gold flash since 1962 but it hasnt been used since 1966! Could you please advise me which spark plugs replace the old Champion L7 's.NGK are available locally, but the supplier doesnt know the replacement number would be correct.Thanks.Mike
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NGK B7ES
From here:- http://www.sparkplugs.co.uk/pages/pricing/ccp/spark-plugs/ngk-x-ref-ccp.asp (http://www.sparkplugs.co.uk/pages/pricing/ccp/spark-plugs/ngk-x-ref-ccp.asp)
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DO NOT run B7ES's in an iron head. They are long reach (19mm) plugs and iron head BSA's use medium (12mm) reach. You want B7HS. I find these hard to get, so I use the autolite equivalent 4093 in my Golden Flasn and have had no probs.
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Beezalex is right, 200%. Don't put B7ES in an iron head, no way, never. B7HS will be fine if you can get. Otherwise, the plug equivalent guides on the web will tell all and more.
There is some prejudice against NGK out there, on the grounds that they seem to fail inexplicably. And they do. There are those who would travel quite a few miles to avoid them. Personally, I use them in some things, but carry other equivalents as get-you-homes if necessary.
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I don't like NGK plugs at all in Pommy bikes. I use Champion but I have some KLGs which work fine as well.
Use Champion L85 in the iron head.
Trev.
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I've not had any problems in using BP6HS in both A10s and A7 Star Twin.
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Just to be sure I didn't miss anything my-own-self, B7ES is correct for alloy head, right?
Richard L.
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Yep,use the B7ES on my A7SS spec.The champion alternative is N4C.
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I've had no problems running NGK's, but that said, I usually run autolites in my flash 'cause the medium reach NGK's (or any other brand for that matter) are getting hard to find in higher heat ranges. I'm sure that if you're running standard compression, even a hotter plug like an B6 would be OK, but in my case the volatile combination of 8.25:1 and iron head makes me seek out the coldest plug I can find.
And yes, Richard, all BSA alloy heads take long reach plugs, so B7ES should be fine...that's what I run in my commuter royal star and never had a problem with them.
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"I don't like NGK plugs at all in Pommy bikes."
Presumably Trev, you mean that you don't like NGK plugs in our wonderfully crafted pieces of fine engineering which were made with such skill and dedication here in Great Britain ?
BTW, What do you do if you get a plug oil up, throw it on the Barby ?
*smile*
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Andy, of course I throw it on the barbie, it is usually hot enough to burn all the oil out. Adds flavour to the snags and chops while we stand around with a stubbie in hand discussing the finer points of British motorcycle engineering.
Trev.
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I have nothing philosophical against Japanese electronic and electrical components, having used NGK plugs very successfully for many years in Japanese and Italian bikes.
I'm familiar with their numbering scheme and they're cheap and available.
However, I've had to stop using them in my Boyer-sparked A65 and my Lucas mag-sparked A10 because they inexplicably fail for no apparent reason. I have fought missing and hard-starting problems for days on these bikes, and had them quickly recur, only to find that they went away permanently when I switched to Champion N3 and N4 plugs.
I don't know the reason and haven't got the time or inclination for a science project; I just know that I'm hassled, in the shop, and fettling when I use NGKs in these bikes, and out riding when I use Champions.
The two Guzzis seem to digest NGKs very well and they run in both of them.
Go figure.
Lannis
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'Tis a mystery - but almost every classic web site has a similar thread about NGKs. Some say it's because the European market is supplied with NGKs from the, er, French factory and that the ones from Japan are 'better' somehow. But the tales of inexplicable failure are legion. Some genius will probably explain what it's all about one day . . .
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Ive never known what it is that actually goes wrong on a spark plug, although its happened to me (And they have been Champion).
Threre's not exactly many parts in one.
Isnt it just a bit of metal rod down the middle of a piece of ceramic?
MN
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Plugs go bad basically because the makers are selling them for almost no profit and hope that with continual failures of conventional plugs you will be encouraged to upgrade to the much more profitable "exotic" plugs.
In real terms standard plugs are about 10% or the price that they were when I started buying them in the 60's.
Add to that the fact that old plugs were designed to burn real petrol which burnt clean and modern "fuel" has all sorts of rubbish shoved in there which leaves all sorts of weird deposits on the plugs that they were never designed to compensate for.
In the old days each & every plug was tested prior to being labeled with the best ones being labeled with the makers name & sold in individual boxes and the worst ones getting a supermarket brand & being sold in multi blister packs.
However modern machines and more uniform materials means that there is little variance in the plugs as they come off the line so the "testing" is simply a work or dosn't work test and the lable is what ever contract they are doing at the time.
Regardless of the brand I have had plugs that failed almost from the first revolution of the engine while others have run for years without any problems.
With new plugs the rule seems to be if they work, do not touch them, don't clean or gap them after installed and they will run almost forever and if they go bad toss them away and try another.
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Funny...I also have a theory about why plugs fail: They're like fuses. If they blow, there's something wrong in your system or you're using the wrong heat range of plugs. If you're running the right mixture and the right heat range of plug, any commercially available $2 spark plug will last thousands of miles. I ran one set of B7ES plugs in my Royal Star for 18K miles until one of the coils started to go out. The only reason I replaced the plugs was because they were the easiest thing to replace once I experienced a misfire. My '69 VW hasn't had the standard Bosch copper plugs changed in at least three years and 22,000 miles.
The only times I've had plugs fail is when a) they got fouled or b)I had excessive pinging. The first instance is probably the most common failure mode because the conventional wisdom in Britbike circles is to run too rich. Set the idle too rich because the choke slides have been removed...run too rich on the needle because the needle jet is worn...run too rich on the mains because you're afraid to hole a piston or you think more fuel will make your bike faster... I would say at least one of the above is true for 90% of vintage bikes out there. And then we wonder why plugs foul?
I did, however, once have an interesting failure on my golden flash (bear with me, there's an interesting punch line coming). When I was first getting to know the bike, I took it on a long ride in the mountains and it was pinging something awful. The combination of the DPO putting 8.25:1 compression pistons in it, my running too hot of a plug and the timing being too advanced resulted in the bike going on on cylinder during a particularly strenuous climb. On the downhill sections it would occasionally go back to firing both cylinders, but as soon as rpm's dropped below maybe 3000, it was back to a 325 cc single. After letting the bike cool down (it was VERY hot), I pulled the plugs and noticed that on one of the plugs, the electrode was MISSING. It had actually broken off. Replaced plug, took it easy on the uphills and got home just fine. As I said, timing turned out to be too advanced and the B6HS plugs were too hot for the circumstance.
I guess the moral of the story is: take the time to make sure your timing is right and your mixture is correct. The best way to do this, IMHO, is to read your spark plugs. I don't mean that garbage about "chocolate brown" in the chilton's manual, but a PROPER plug read. Here is a great place to start learning if you don't already know: http://www.strappe.com/plugs.html
Cheers...