The BSA A7-A10 Forum

Technical => Lucas, Electrical, Ignition => Topic started by: bsapete on 05.12. 2018 01:16

Title: Spark plugs
Post by: bsapete on 05.12. 2018 01:16
Hi Gents,
What’s the concensus regarding spark plugs? Is NGK the preferred brand of those in the know?
What would be recommended for my Spitfire Scrambler?

Title: Re: Spark plugs
Post by: mikeb on 05.12. 2018 02:46
there is no consensus. its like is fish better than chips. or chocolate better than ice cream. or beer better than wine. ok cancel that, this is agreement about that amongst bsa owners on that one.

but not on plugs. some people argue strongly either way.
with the alloy head (super rocket - same head as some spitfire scramblers?) i run bp7es ngk to good effect. the 'p' means protruding electrode which may help a bit with mags where the spark is not so strong (compared with moderns and using modern oily fuel). bp6es is a little hotter on the ngks if the 7 is too cold - try it and see.

the one things people do agree on is cleaning modern plugs is irksome/pointless and they foul up badly due to the unglazed porcelain. so buying new ones is a common occurrence whatever your brand. and never buy 'R' ones with resistors in them with a mag.

there's heaps on threads on this topic - try the search button above.
Title: Re: Spark plugs
Post by: duTch on 05.12. 2018 03:18

 Yep- fairly much what like said....but I've been trying BP6EY (same as except electrode is notched) there's plenty threads, in fact there was one not long ago also titled 'Spark Plugs' so I thought out was a continuation but worth a look....I may need tho revisit it myself and check that I posted an outcome
Title: Re: Spark plugs
Post by: groily on 05.12. 2018 07:51
Consensus? No way!
But I've never had any problems with B6/7/8ES in alloy head bikes or B6HS in the iron head of my A. Then nor have I had problems with N4 and N5 Champions, or Bosch. I hardly ever replace plugs as they seem to do well - as long as they come from known-good sources. And I've never gone for fancy ones with iridium tips, long noses or any of that. As long as things start first kick and run well, I let well alone!
What seem to be forgeries are all over the place though. A mate came round the other day with 6 plugs he'd bought from some sort of online seller, and only 1 worked at all on test  . . . 5 were completely dud right out of the box. Tells us something, but not sure what.
There are threads on here I think saying how to identify the real thing from the pirated versions - I just buy from trusted sources and maybe pay an extra small amount compared with e-prices.
Title: Re: Spark plugs
Post by: muskrat on 05.12. 2018 08:35
G'day Pete.
Always NGK for me in everything. Both my BSA's are alloy head and electronic ignition. B6 or 7ES in winter, 7 or 8 in summer. A hotter plug (lower #) will burn a rich mixture better but be careful if the plug is too hot as it will start easy in the morning with a carb tickle but later when the bike is hot the plug may fail or worse.
I've never had a problem cleaning plugs. I have a cheap sand blast type plug cleaner
Title: Re: Spark plugs
Post by: BSA_54A10 on 05.12. 2018 08:49
The new NGK's do not have any glaze on the insulator.
This allows crud to adhere and if you clean them with a wire brush, streaks of metal making a conductive path.
New plugs should be burned clean.
I use the oxy with a very lean flame and the 00 tip.
Like the others always use the projecting electrode that is the P in BP7HS .
I have found that if the engine is turned off after less than 20 minutes running the plugs load up when you try to restart.
This is because modern fuel is conductive at cylinder pressure.
So if we are going 5 minutes don the road to get fuel I starve the engine off.
Title: Re: Spark plugs
Post by: bsapete on 05.12. 2018 10:53
Thanks for the advice fellas.
I’ll give ebay a miss and pick up a pair from my local auto shop.
Better chance of getting the real McCoy I suppose.

Title: Re: Spark plugs
Post by: Slymo on 05.12. 2018 20:41
I think the inability to clean is more a result of the carbon deposited by the modern unleaded fuel. If a plug fails due to rich mixture the carbon deposited is incredibly conductive and traditional methods of cleaning are futile. What I did discover once by mistake is that when testing the plug with a mains powered megger I induced an arc in the plug which briefly lit up the workshop. It lasted a few seconds and then once it stopped the plug returned to infinite resistance and was once again usable.  Not good for the megger though.