help with ex George Cohen ES2

... you have there Luke. Sorry can't help with the question.

It would just be an ES2 if you take away George's work. 

What are you trying to address? Is the ignition causing you problems or do you have charging issues?...   which makes it less reliable.  It is a great bike, I remember it in George's hands; I called at the farm one day; he was out said one of the girls.  But he won't be long, I can hear him coming out of Chillingford!  you could here it coming for miles! 

Are you rebuilding to address the leaks or is she worn?  Maybe if just needs resealing / tightening up?

He must have wanted to find out if there was any benefit from twin plugs.  But he could not fire a twin plug/twin spark setup with a normal magneto, since the spark would always take the easier route and only fire one of them.

So he had to fit the Boyer system to test it.  Boyer for Commando always fires two plugs at the same time (wasted spark).  If both leads were fed to different plugs within one cylinder, they would fire both of those twin plugs.

He probably found no improvement, so he went back from the electronic ignition to a racing magneto instead.  And of course it doesn't require a battery + coils + charging system, which saves a little power and weight and makes it a bit more reliable.

So the only evidence remaining is the unused second plug.  It makes perfect sense.

If all of us took our Nortons apart to slow the leaks, there wouldn't be very many on the road!

Typical of George to use a belt drive for the magneto!  When you think about the way George used to dismiss the virtue of Originality, that's perhaps not surprising...but he still loved Castrol R!  (Now no longer made...I suppose the Morris version is the replacement...)
My two singles are both incontinent...I don't even knoe for certain where from.  Gearboxes do need regular tipping up.

Fit an air cleaner, you do like your engines don't you! 

Hi Luke,

   Your bike is perhaps better described as a Model 18 as it has a rigid frame, although both models share the same engine with the only difference being the stamped numbers.
   Looking at the engine, the barrel looks to be a 500T which has had a couple of fins removed from the top. This would indicate the stroke has been reduced and if it has DOHC Jawa speedway flywheels, this would be 81mm. The bore size of the Jawa would be 88mm, but the maximum safe size for the Norton barrel will be 84mm, so it is possible the piston is a BSA B50 which would make the capacity 449cc.
   Regarding the oil leaks, make sure the return flow seen in the top of the tank is the expected amount and also there is not too much oil going to the rocker box. Also looking at your photo there are not enough engine breathers for a high revving engine. If you look at a Manx racing engine you will see these have 3 breather pipes on the crankcases along with the timed main bearing breather. One-way breathers are not an advantage, it's better to let the engine breath freely in both directions, but you will need a catch tank.

I knew George well and was around when he was building his various Specials both pushrod and ohc engined bikes .  I did sell him an ex Shane Lockley ES2 pushrod race engine in a moment of weakness , this had a special crank , JAP conrod, B44 piston , race cams and that went into one of his Specials.  I can remember seeing George machine the distinctive reduced finning on the engine . There's some information on his Specials on the internet under the heading " Tales from a Somerset Shed". George normally supplied useful and detailed build notes with the bikes he sold .   Hope this helps.