Norton jubilee timing advance

One spring?
Go EI AND 12v.

You want to run around on a pair of springs, one 60year old another (probably made by another company) new. Sounds like a recipe fo a dodgy advance result.

Go electronic, you'll not regret it and it's reversible
Dan 

I agree with Al and Dan Graham, converting my Navigator to 12v and Pazon electronic ignition and my Electra to the same ignition system completely transformed the bike making it start easily and tick over like a Swiss watch, run far smoother, cooler and more powerfully.  It is far easier and quicker to set the ignition timing than the quick wearing and inaccurate points and Bob weight system which is vital for good performance and mechanical reliability on all the Leightweight twins.   It is by far the best improvement I have ever made to either bike at very reasonable cost.  Good luck, a well sorted Jubillee is a joy.......although the brakes are at best marginal!!!  Nick

Marginal Brakes-quite a useful item! This makes you reappraise your 'road'. If you cannot stop then make sure you are travelling at the right speed for the conditions. Having done a few miles all year round we understand the damp and greasy roads which start now!!! You do NOT brake on wet/greasy roads (well you do once-you fall off-it hurts-bends the bike) you learn not to do it.

With a contact breaker you stand a fighting chance of getting the timing the same on both cylinders.

Never the less, I agree with the other posters here, 12v and EI are the way forward.  I have given some thought to the idea of being able to independently adjust EI for each cylinder, presently no further forward then idle musings.

John, Can you explain why you would want to have different timing on each cylinder?
The joy of the electronic ignition is it will always be equally correct or equally incorrect on both sides.

Well if you have different compression ratios on the two cylinders, perhaps with two different height pistons, then of course within a couple hundred miles the points/springs will wear and the ignition timing will have to be reset on both cylinders, again and again. Perhaps the rider likes the vibration and is looking forward to the next rebuild that is due very soon.

... what the different advance figures for each cylinder would be? I agree with others that having identical curves for both is the way to go,

John,

               errors in the points cam and so on ?

Not with electronic ignition. That is the 'point'.

I have checked timing on a lightweight, fitted with Pazon, from idle to fully advanced. 
An 8 inch timing disc was secured centrally to the crankshaft. Graduated in degrees with 1.7 mm between degrees. 

The pointer was nice and steady, in the strobe light, within a 2mm range at all the speeds investigated which I considered pretty good. 

My light was triggered by one HT lead which was alternately delivering one spark from the left hand Pazon pick up coil, followed by spark from right hand pick up coil etc.. 

Backlash in the timing gear train can contribute to a fuzzy pointer position. 

So, on my sample size of one, ignition timing seemed steady, not much affected by timing gear wear, and the two pick up coils are 180 degrees apart on the pcb. 

EI. Fit and forget. 

Peter

"one HT lead which was alternately delivering one spark from the left hand Pazon pick up coil, followed by spark from right hand pick up coil etc.. "

On the electronic kits I've seen, the two magnets and two trigger coils generate one AC sine wave that signals the black box to trigger a spark at both plugs BTDC.

The two HT leads spark at the same time 'wasted spark'. This is the result of Boyer Brandesden and/or Pazon ignition on ALL twins. Any minute variation due to wear, machining tolerances are so small they can be ignored.Any thoughts that these ignitions can have the pulse between the two cylinders altered is to be forgotten due to the way the system is made.
Please do not use the term 'AC sine wave' with regard the Pick up pulse, it is to be thought of as 'one pulse'.
The idea that we can get the timing 'right' with twin points, is just a 'sales gimmick' from Lucas.
The points and advance retard mechanism (both recipients of vibration) will alter the timing within moment of starting the engine.
EI-fit and forget! Remove the constant fiddle with points!

Yes, points are trouble and Norton Jubilee points were more trouble than most.

And- one of the good aspects of the common electronic ignition kits for Brit twins is the always identical timing on left and right cylinders.