1952 Norton ES2 spark plug

[iansoady]

I generally consider myself quite competent with old bikes but confess to being flummoxed here. All the handbooks for my ES2 including the one by Edgar Franks who was responsible for much of the design detail, suggest that it should have a 1/2" reach plug (Lodge H14 etc). However, the threaded hole in the head is 3/4" long and a standard long reach plug fits fine without hitting piston crown or valves. Cast iron head by the way.

I can't imagine that such an error would have been perpetuated (but having written user manuals myself I know how an incorrect statement can be carried over from version to version). But if I fit a short reach plug, (a) the spark will be happening far from where the mixture is, and (b) the lower threads will get caked in carbon.

I'm still at a fairly early stage with the engine and have just correctly timed the ignition (which was 5/16" BTDC instead of 5/8"). I haven't run it with this setting but when I started it on the 5/16" position with a short reach plug there was lots of missing. Not carburetter as I've gone through that carefully.

Any observations?

[mini-me]

5/8 is a lot of advance for modern fuels; I happily run on 3/8 on a pre war 500. even 5/16 ought to be ok, I reckon 5/8 advance is an ankle breaker.
Older Bikes,esp singles  run smoother on less advance and give the bottom end an easier life.



I have come across the plug length conundrum as well,  my bike seems to run /start happily on it. Also an iron head.

If it bothers you surely just use a long reach equiv of H14?

[chaterlea25]

Hi All,
I tend to set the timing on old engines by setting at TDC on full retard
The advance on the lever to find the best running position.
Then readjust that to the full advance position
I have just finished a 23 HD and set it like that, I have all the HD handbooks from 1919 to 29 and the timing figures
changed to give more advance every couple of years, I'm presuming that was because the fuel was improving in quality
through those years

John

[R]

Yes, all the books are wrong ? on the ES2 sparkplug from that era, even the handbook supplied with each new machine back then. It takes a long reach plug, like you say.  There doesn't seem to be any reason why the quoted plug is down a deep dark hole, although it works better than you think it should, it seems.

This has been discussed all over the place, and I found this out again just recently when a shop that has been in business for many a year supplied me a plug for a 48 ES2, without any numbers actually being quoted. When I commented that I was expecting a long reach plug, I was advised that thats what they have been supplying off their chart ever since these bikes were new !!
Hmmm.

[33d6]

In vintage times it was common practice to hide the spark plug in a deep hole away from the combustion chamber. As with every thing else back then spark plug technology was on its infancy and oil fouling was a problem. Plugs were positioned to avoid oil fouling and down a deep hole was a simple (and cheap) solution. Your ES2 engine was designed in the 1920's so is a relic from those days. Ride vintage bikes and you will often find spark plugs positioned thus and all working quite well. You can fit a long reach plug if you wish. Modern spark plugs are much improved over those from the 1920's It will make no discernible difference.

You've also received good advice about the timing. Personally I go along with Chaterlea25 I prefer his approach but that's just me.

Can we see a photo of the finished beast? I think the ES2 was at its peak in that plunger sprung frame era.  Lovely bike for just loping along at a steady 50-55mph. Like being on a steam train.

[iansoady]

Many thanks all.

I agree 5/8" does seem a lot - it equates to 42 degrees or so but I'll try it at that and see how it goes. Possibly after breaking my ankle......

The plug issue came to light when I bought one from the Green Sparkplug Co, which was short reach which I wasn't expecting and then checked in the manuals. I have a suitable long reach item to use. There was a thread in the NOC forum but it petered out with no firm conclusions.

I'm taking my time over this (and holidays and enjoying good riding weather keep intervening) so it will be a while before I can show any improved photos. This is the tank (before and after) which I painted and lined during the winter. I have fixed the slight bleeding of the lines!

[cardan]

In vintage times it was common practice to hide the spark plug in a deep hole away from the combustion chamber...

My favourite is the EW Douglas (350 side-valve twin) from the late 1920s - the plugs are well masked down a hole, and the ignition timing is a staggering 50 degrees BTDC!

Leon

[L.A.B.]

I agree 5/8" does seem a lot - it equates to 42 degrees or so but I'll try it at that and see how it goes. Possibly after breaking my ankle......

1947-58 ES2 is 0.375" (3/8") according to Roy Bacon's Norton Singles book.

[R]

The Owners Handbook says 5/8" for the ES2 and Model 18,
(and 7/16" for the 16H and Big4) 1948-54.

I'd say to set it there, you can always back it off a shade if it doesn't like it or runs hot.
If you run it retarded though, it will likely run hot(ter), and if you can't advance it any more,
it may not be good...

I also have a prewar ES2, and it has a short reach 18mm plug in a short reach spark plug hole,
so Nortons seem to have known what they were doing then, no deep dark holes then.
It hasn't done any miles yet either though, so we will see.

[Rex]

Think I'd believe the Norton book over anything Bacon says, although less advance seems better for modern fuels.

[iansoady]

Yes, I have the Bacon book but I suspect that 3/8" figure is a misprint. Both Edgar Franks and WC Haycraft say 5/8".

The Bacon books are quite good but do need some careful interpretation on occasion.

We'll see how it goes (or doesn't). I'm sorting out a prop stand at the moment being disinclined to spend well over £100 on one of Mr Emery's specials, which would probably fit about as well as his other stuff.