Update on timing from the timing side.

Ian could this setup be adapted for commandos? Would make setting the timing a one person exercise.

I'd suggest a thinner line and a sharp pointer, your line must be.a couple of degrees at least! 
Dan 

Ian could this setup be adapted for commandos?  Question?-as the Commando has a timing 'disc' built in then timing is not hard. And if for any reason you did use this method and the timing chain was a bit slack then your timing would be based on the  camshaft position. Timing on the primary side would be timed to the crank shaft.? Is this a good idea?

although the Commando does have a 'built-in' disc, it's still on the opposite side of the bike and thus not that easy I found. My BSA Triple had the alternator (and thus the timing marks) on the same side as the points/EI stator which made timing with a strobe a doddle.
         I always used to alter the timing by turning the crank forwards and then back as necessary to ensure that any chain slack was taken into account - seemed to work OK.
 

 I always used to alter the timing by turning the crank forwards and then back as necessary to ensure that any chain slack was taken into account - seemed to work OK...... You can't do that when it is wizing about with a strobe looking at it. So my question still stands, this timing gubbins might work well on the lightweight with gear driven cam drive but located on the cam on a commando?

I have doubts as to whether or not this set up is accurate enough to do the job.   Degree lines on the plastic rotor will be, if I've done the maths correctly, will be 0.43mm (0.017") apart at a radius of 25mm.  

A fine pen line will be about 0.4 - 0.5mm apart.

Therefore, it will be difficult, if not impossible to see what's happening when its spinning around at speed with a strobe.

How is the plastic rotor located? it needs to run true for accuracy, any wobble will introduce another inaccuracy.

For accuracy it would surely be better to do the job with a decent size timing disc mounted on the crank shaft?

Having owned an Electra, I can say that it is well worth having a go with your method. It is certainly a fairly major job to actually get at the alternator to fit a degree disk.

Also, you should have a very steady strobe flash without any jitter, you are looking directly on the end of the thing causing the 'spark'.

Even with the best of setups, there will always be slight jitter when you are looking at the alternator. On the Commando, the cam chain. On the Electra, the gear train.

I like the idea of being able to time from the RH side, the only drawback I see is the fact the disc is at 1/2 speed so needs that little bit more care during strobbing.

My thoughts are, why not modify a normal timing disc to attach to your rotor adaptor, only needs a couple smallish screws. Also if you cut out apertures you will be able to access the adjusting screws behind the disc. I know you can't use this while the engine is running.

You can still use this to set accurate TDC with the advised piston position tool, I made mine so by adding/subtracting washers it actually stops at 24deg each side, handy for my Navigator but could be any degree you wanted.

More food for thought,
Stan

I stand by my comments that the OP's setup will not be accurate, far too small in diameter to be of any use.   If lines can be engraved on it at 1 degree intervals, they will be too close together to resolve accurately at speed.   To put this in to context, look at the 1/64" lines on a steel rule, best looked at, with older eyes, under a magnifying glass, and that's with it not moving, let alone spinning around at 3000+ rpm.   Also, being plastic, it will never be consistent in attachment.

Sorry fo being so critical.  I don't like doing that without offering a viable alternative. So, here goes.

The use of a large diameter timing discs is an absolute necessity for accuracy.   Why not attach the disc to the timing cover with the two screws that fix the points cover.  There is, what looks like a machined surface that could be used for accurate location.  A carefully machined metal adaptor between disc and cover.  The centre of the disc can be cut away to get at the stator for adjusting.

Then make an extended bolt to hold the rotor.  The extended end of the bolt could then carry a pointer. This should be made in such away that its (radial) position is adjustable to help with the accurate finding of TDC.

How does that sound?  Disc stationary and pointer spinning might fly in the face of convention but will work.  It's a way I've seen described in a Ducati manual.

Since this idea of timing (strobing) from the timing side of the Electra engine was first proposed because of difficulties in attaching a timing disc the the crank shaft I've been able to to have a look at some of the starter components.   I think it should be possible to do this without removing the starter mech.  Modification would be needed to the parts, nothing drastic though.  The stationary disc, revolving pointer may well be the way forward here.  

The big advantage of timing from the timing side is the need to disturb an oil tight joint is eliminated.   To this end I modified a badly corroded and cracked primary chain case cover to get access to the end of the crank shaft (and clutch adjustment).  Sealed with a threaded plug and O-ring.   I had two reasons for doing this, one being for accurate ignition timing. 

Sorry for the long post.  

8 thou easy to see?  You must have fantastic eyesight!  How are you going to mark the disc?  That's some very fine lines to create to be able to differentiate between degrees.  That, I think, will be near impossible to do on plastic, steel or aluminium for the rotor would have been a much better choice of material.  The static pointer will need to be very fine to pick up each division.  

How are you going to use it to find TDC with your set up?

If you are prepared to remove the cover, I can see a couple of ways of attaching a disc to the crank without disturbing the starter mech.  Would require some modification to the existing parts but very doable.

Peter, what I had in mind was to drill a hole through part No. 24752 (from GA drawing).  This hole would be as large as possible, 1/2"?

This would give space to fit an extended bolt (24759) or a bolt with a threaded internal bore.  This, I think, would be okay for a pointer or timing disc without the need to dismantle the starter mechanism.  My approach to this job would to be to make the part(s) from scratch, if possible, rather than modify, just in case something went wrong!

This means removing the cover to set or check the ignition timing, something the OP wants to, in my view, quite rightly avoid if at all possible.   My approach would be to create access through the cover, a welded boss and threaded plug.  May depended on the availability of an unmolested cover.

Changing the subject, slightly, my interest in Electra's has been piqued by a friend who has an Electra engine minus the starter.  Just the primary chain case and the casting that supports the the starter sprocket/ratchet.  We have looked into using modern tech to replace the original parts (if they were there!).   When this project might happen, no idea.  He's happy with kick starting, but who knows what the future might need?

This topic has been very entertaining. When I got my driving licence and could only afford basic transport ( first car a triumph herald ) I had to learn how to maintain high mileage cars.In those days I always carried a spanner in the glove box which I used to adjust the distributor.
I learnt how to interpret the state of tune of my vehicle through listening and the "feel" of the engine.No strobe available. This along with points adjustment was an ongoing service requirement.
 Over the years I have converted all my twin cylinder bikes to electronic ignition.
I hope Ian's timing side method works. Even if he is half a degree out, will it really matter?