As anyone with one of these machines will know they should take a long reach 18mm sparking plug. Even in the 1970s they were hard to find but I managed to secure 6 of them in total. However, after all these years and running the machines through the 70s, 80s and 90s, I am now down to my last 2 long reach 18mm plugs.

For those that continue to run their 16Hs and SWD Big 4s what are you using and importantly where do you find your sparking plugs. I know both machines will run with the available short reach 18mm plugs but I have never been keen on using these as the spark is slightly recessed from the chamber which does not appear ideal.

Advice and guidance from those who run their machines regularly would be appreciated.

Thanks.

I search around and pay silly money for New Old Stock. Either the M80 or currently a KS5 KLG. They're only a nominal 1/2" reach though. What have you been using ?

Rik - I will have to go and have a rummage and see what I used. I am not even certain they were named but it was over 20 years since I installed the last one - I do recall however, they have pink porcelain bodies and are not two part as the KLG plugs. More information to follow.

Keith both the B4 and 16H manuals quote the KS5 or M80 as Rik pointed out which are only 1/2" reach. But they also quote the gap as being 20-25 thou which is bigger than that quoted for most other makes (ie 18 thou)

Ron

email (option): ronpier@talk21.com

You could machine an adapter to screw into the spark plug hole and then change to an easily obtainable 14mm plug...I did that for my G14 BSA...Ian

email (option): ian@wright52.plus.com

You can buy the adapters quite cheaply on ebay

https://www.ebay.co.uk/itm/1x-Spark-Plug-Thread-Adaptors-18mm-down-to-14mm-Brass-M14-M18/232637022008?epid=1143522865&hash=item362a3f3f38:g:1XcAAOSwoFVaYzso

I found a NOS Big4 cylinder head at Netley some years ago, but it had a chunk broken out of the plug hole, Ian had it machined down flat for me so I could use an adapter, I did wonder whether just to use a short reach 18mm plug but the machine is still in pieces so I haven't had to make a final decision yet.

Rob

email (option): robmiller11(a)yahoo.co.uk

Pink sounds like Lodge Keith! Ron

email (option): ronpier@talk21.com

If they're pink then they're almost certainly Lodge. Unlike KLG, they retained the same type code when changing from mica to their 'Sintox' insulator. They always seem to have been 1/2" reach.







I only have mica H1s in my collection. Definitely 1/2" reach.

I use the Lodge plug in my 16H, I've taken it apart and fitted a new copper crush washer between the 2 parts. Other than that there's not much to go wrong with a solid metal core and 3 electrodes. I also have a 14mm adapter when I go away, so I can fit any long reach modern plug if needed.

email (option): horror@blueyonder.co.uk

I ran my 16H for years on NGK A6 18mm plugs without any issues at all....

I haven't used the bike for a few years now but I have a stock of new KLG M80's plus Lodge and Champion types to play around with when I get round to it....

Most decent autojumbles produce new old stock 18mm plugs and it's always worth checking out industrial engine and Garden Machinery/Lawn-Mower specialists, in particular those who've been around a few years and may still have stocks of or sources for 18mm plugs......