Champion spark plug for 1939 16H

Glenn,

i don't know whether there was any change from the 1937 spec but my WD16H is running an NGK A8, a comparison of alternatives is available on this link. http://www.gsparkplug.com/shop/ngk-a8.html

From memory that was the equivalent to original spec, or as near as i could get at the time.

But on the head which was on my bike this is too short a plug - when fully engaged the plug tip doesn't project into the combustion chamber. I have a spare engine of similar age and on that head, which otherwise looks the same, the plug is spot on - the tip projects below the surface of the head.

Nearly forgot, i have been told by someone who should know that i am probably running a colder plug than is necessary, one hotter was recommended for general use. The current one perhaps for sustained open road work. I haven't done enough miles to get too concerned.

Hi, I have the same thoughts, a short reach 18mm 1/2" seems really short to me and a3/4" goes into the head a bit! What to do ?

Previously antony_ryan wrote:

Hi, I have the same thoughts, a short reach 18mm 1/2" seems really short to me and a3/4" goes into the head a bit! What to do ?

What about fitting a copper washer to space it out.

The book plug for prewar 16H is KLG S1. This is 18mm. WD Norton was listed with KLG FE70 which is 14mm. So the WD Norton engine is actually different from the 1937 engine even though all the books say it is the same.

I don't know the modern equivalent - I can't find KLG S1 on the internet. I do know my bike is running but can't remember what with. I'll look later - and check what others are using at Brooklands (Surrey NOC) today.

Is this link any help? Says 18mm for WD...

http://www.wdnorton.nl/Spark_plugs.htm

The cylinder head part number (9111) remained unchanged between 1936 and 1938/39 together with wartime production. The parts re-numbering in 1946 makes a comparison difficult but a '46 engine that I had appeared to have the same head.

The plug referred to in the technical section is likely to relate to the 1948-on alloy head models.

The pre-war mica KLG KS5 gave way to a detachable porcelain M80 and then a one-piece plug, also coded M80. I've seen these with both 7/8" and 1" hexagons.

I have examples of all of these plugs and they are all 1/2" reach, measured without the sealing washer so a little less in practice).

I have a number of heads and the threaded depth seems to be either 3/4" or 7/8" - an NOS (and presumably later) head is 7/8" - This might account for why some of them are flyers and the others a little less so....or could there be some 'Trusty Tractor' and stationary engine heads contaminating the gene pool ?

Green Spark Plug supplied me a Champion D9 as equivalent which some sites list as equivalent to NGK A6, A7 and A8 so I'd suspect that exact heat value is not too critical on these.

Previously glenn_osborne wrote:

I recently consulted the spark plug table located in the technical section of this site and ordered the Champion N5 for my 16H without another thought. This is wrong. The N5 is a 14mm plug with a long reach. I need a 18mm and I think a short reach one. Can anyone tell me which champion plug I should be using ? And while we are at it which one for 1938 ES2 ? Thanks in advance, Glenn

Hi Glen,

My 1955 KLG catalogue lists a M60 18mm plug for pre 1947 16H and Big 4's. This has a 1/2 inch reach. For other models requiring 18mm plugs then a hotter M60 is recommended.

My Champion catalogue for 1963 lists a type 16 for the same side valves. The Champion catalogue also lists aa D16 as a replacement for a KLG M50.

For a 1938 ES-2 you need a 14mm plug with 1/2 inch reach. Originally a Champion L 10S (which became an L85) was specified. Use a KLG F70 or F80 (or equivalent) for a cast iron head or FE 70 or 80 for an alloy head. (3/4 inch reach)