BSA Owners' Club Forum

The BSA Workshop => Twins => Topic started by: MARKIE2CUPS on 01 April, 2017, 20:10:47

Title: Which spark plugs to use?? A10
Post by: MARKIE2CUPS on 01 April, 2017, 20:10:47
Hi all, I was wondering what type of spark plugs to use in my 1957 a10 golden flash. My BSA hand book says  L10s but searching on line suggests N4c champion. But also champion L82C which only has a 12.7 reach whereas the others are 19mm. Is the short reach for iron heads? Mine is a alloy head by the way, any help would be appreciated confused lol. The ones that came in the box of bits with the bike were champion n-3  with 19mm reach ( don't know for sure if these were used in it tho )  cheers Mark :-\
Title: Re: Which spark plugs to use?? A10
Post by: JulianS on 02 April, 2017, 09:56:36
You definately need a long reach plug with the light alloy cylinder head.

The N4C should be OK it was selected for the use with higher comp pistons of the Rockets. If you are on lower comp and the bike is unhappy with the N4C then you could try a slightly hotter plug such as N5C.

There are alternative plugs from different manufacurers - I use long reach  Denso W22ES-U in my A10 alloy head. Other riders prefer NGK.
Title: Re: Which spark plugs to use?? A10
Post by: STAR TWIN on 02 April, 2017, 17:40:47
I Use NGK B7ES in my alloy head A10. Be careful to avoid resistor plugs. Not suitable for magneto ignition. Take a look at the Green Spark Plug Co website - lots of info there.
Title: Re: Which spark plugs to use?? A10
Post by: MARKIE2CUPS on 06 April, 2017, 10:08:23
Thanks  for the replies, and now you mention, when it was in bits the pistons are high compression it also has comp valves so guess someone back in the day was a ton up boy lol. Well I've got some experimenting to do many thanks Markie 😂