spark plugs for veterans

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Michael Starr.
Posts: 17
Joined: Wed Oct 12, 2005 10:45 pm
Location: Hertfordshire UK

spark plugs for veterans

Post by Michael Starr. »

I recently acquired a new old stock Champion D7 15 mm spark plug for my 1929 Matchless. I notice that it is a short reach plug, which leaves the spark somewhere in the middle of the hole. My initial thought was that this was no good, but am persuaded by the argument that such plugs were preferred in total-loss oil engines as this prevented them oiling up so often. Does anyone have any thoughts on this? Alternatively I could just refit the 15 to 12 mm adapter and fit a modern long reach plug.
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silverarrow
Posts: 549
Joined: Mon Jan 01, 1990 12:00 am
Location: LEICESTERSHIRE UK

spark plugs for veterans

Post by silverarrow »

Hi Mike,

I presume you have 18mm plugs, i recently bought new old stock Champion 7's for my 1930 Matchless Silver Arrow which were coincidently & were the same well used make/model as was in the engine when i bought it.

It seems that all the plugs i have for this engine is the shorter reach type and leads to same same "recessed" firing position.

This does not seem to adversly affect running at all although it must reduce compression a little compared to fitting a long reach plug.

You perhaps bought your plugs from Tim Green of the Green Spark Plug Co who I think is the best served to give you definitive answers. Tel: 0161 973 6755. Tim supplies a huge range of plugs including the older !8mm Plugs and can help with 18-14mm conversions as well.

Regards,

Les Smith energy.man@fsbdial.co.uk
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Michael Starr.
Posts: 17
Joined: Wed Oct 12, 2005 10:45 pm
Location: Hertfordshire UK

spark plugs for veterans

Post by Michael Starr. »

Thanks Les. I saw Tim at Stanford Hall and he said that fitting a recessed plug should not be a problem - but I just thought I'd check with somebody who'd actually used one! If yours goes alright, then I'll give it a try. When I acquired the bike, it already had the 18-14 mm conversion fitted and a modern plug, but I'd read that the older style plugs were better if they could be found. The simplest way is to try both methods and see which works best.
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