The BSA A7-A10 Forum
Technical (Descriptive Topic Titles - Stay on Topic) => Lucas, Ignition, Charging, Electrical => Topic started by: Nomad54 on 17.09. 2025 18:56
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Almost finished the rebuild of my
A10 alternator model 1963. What are the best spark plugs to use. It has 7.5 to 1 pistons and an alloy head fitted as the cast iron head was to far gone.
I have heard some stories about ngk plugs so looking for best advice.
Tom
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N3 Champions or NGK equivalent are fine. I actually have one of each in mine and have for the last 4 or 5 years since one of the Champions broke an insulator in a small town in the middle of nowhere and the local garage only had NGKs. With un leaded gas and a relatively gentle spark they should last forever.
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the local garage only had NGKs. With un leaded gas and a relatively gentle spark they should last forever.
Yeah? I'll be dead by then. :-:
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Ditto *sad2*
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had a lot of fouling with NGKs switched to Champion N3c been good ever since .....NGK has an article on their web site how to spot the Chinese copies
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G'day Tom.
I've only ever used NGK's in everything (BSA's, Honda's, HD's, mower, chainsaw etc).
If a plug is fouling try a hotter plug, say go to a B6ES/HS or even a B5ES/HS or a BP6ES/HS (protracted electrode). ES for alloy head, HS for iron head. 7 is standard but I run BP6ES in the 51 A7 and BP8 or 9ES in the A7 racer.
Don't buy plugs off Fleabay only from a reputable supplier.
Cheers
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Don't buy plugs off Fleabay only from a reputable supplier.
Australia may well be different, but in the UK most local automotive shops have dissapeared. And those few that remain tend to stock a very limited range of plugs. So, it's not so easy to find a reliable outlet. Buying from internet old bike specialist is the safest option, but that has the disadvantage that sometimes delivery can be quite slow.
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NGK B6HS for me. No problems after many 1000s of miles in the GF, but I have had a bit of a cough, splutter and hard starting of late (the bike, that is). Will change the plugs and check points/HT leads which should sort the problem.
Have used NGK for 45 years with virtually no problems.
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NGK B6HS for me. No problems after many 1000s of miles in the GF, but I have had a bit of a cough, splutter and hard starting of late (the bike, that is). Will change the plugs and check points/HT leads which should sort the problem.
Have used NGK for 45 years with virtually no problems.
Excellent - for iron heads Worty.
When did your mag last get properly looked at btw - just wondering from your recent posts about starting trouble?
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NGK B6HS for me. No problems after many 1000s of miles in the GF, but I have had a bit of a cough, splutter and hard starting of late (the bike, that is). Will change the plugs and check points/HT leads which should sort the problem.
Have used NGK for 45 years with virtually no problems.
Excellent - for iron heads Worty.
When did your mag last get properly looked at btw - just wondering from your recent posts about starting trouble?
Aye, iron head - non of these new fangled ally heads for me.
The mag was from CB a couple or three years ago (I think, probably longer). I believe it had a replacement condensor (can you confirm CB?).
When the original mag went, it started off with similar symptoms - bad/erratic starting, a bit of a splutter here and there, and the occasional 'pop and stop'. However, tickover is generally fine and also fine at higher revs/speeds.
Hope it isn't the mag. Bergs got the bike timed up beautifully and I hate doing that job!