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[Micah]

Hi, can any one point me in the direction of info on the magdyno on a 1947 model G? Specificly i want to understand the purpose of the manual advance/retard. How do i know if the timing is right? etc. I know absolutely nothing about this. any help would be much appreciated.

thanks

[papasmurf]

The petrol/air mixture explodes at a constant speed no matter what the speed of the engine.
So at slow engine revs the explosion needs to start to take place close to Top Dead Centre, with the piston on the way up (fully retarded) because the slow speed of the piston.
A high revs, faster piston speed the explosion needs to start to take place when the piston is further away from TDC on the way up, (Advanced.)
It is vital that with manual advanced/retard systems that the ignition is set to retarded to start the engine or a back fire or kick back will probably happen with the emergent properties of foul language and bruising to the leg.
It is also useful to retard the ignition slightly when slogging up steep hills in high gears and mid range revs as the engine will pull better.

[Micah]

Thanks for the quick reply. Just to make certain, is the advance when the lever is pushed forward? I havent had any problems starting it in this position. When i pull the lever back the motor slows until it stops.

[papasmurf]

Micah you will have to wait until someone else answer that question because some makes of British bike run on tight cable advance and some run on slack cable advance.

[vince]

if cable enters rear of magdyno the lever has to be pulled to advance ignition . if cable enters the front (near the barrel)then lever has to be pushed shut to advance. In practice keep it fully advanced except when idling. if pulling up a long gradient slowly retard until you reach a point when engine responds better, dont forget to advance again at the top, Its a bit of a black art but you soon get the feel of it.

[Mark M]

Enfields are usually slack wire advance, that is, lever pushed all the way forward is full advance but do check the magdyno because as Vince says as it might have been changed in the past.

REgards, Mark

[Adrian]

Looking at the timing side of the engine, the steel drive gear on the magdyno/magneto/contact breaker drive rotates anti-clockwise on the Bullet (as does the exhuast cam gear and the first idler gear), so on the other side of the bike at the points, the rotation will be clockwise. Moving the cam ring on the magdyno anti-clockwise will mean the cam meets the points sooner and the ignition will be advanced. Moving the can ring clockwise means the cam will open the points later and the ignition will be retarded.



In view of the information supplied in the previous posts, pop the points cover off and check to see EXACTLY what happens when you move the advance and retard lever on the handlebars.



A.

[WDCO42]

Hello Micah, I had a look on my CO (the same engine as the G), and says the same as Adrian : When you have the Magdyno in front of you, the points turn clockwise, so for full advance, the cam must turn anticlockwise. When you set the ignition, normally, the points at full ignition open at 34°, and as related on my workshop manual, 3/8 inch. All that with a 0.12 " points gap. And I confirm too that at full advance, the lever should be slack, with the "left ignition setting cable" magdyno. The good idea, with our "new fuels" is to give a bit more advance, as 36°, and then set the lever until the engine runs smoothly. My (slightly tuned) CO runs happily with a 36° setting.
Hope it will help you
Claude

[Micah]

Thanks heaps everyone, exactly the info i needed!

If anyone wants to add anything further about the particular quirks of the model G, I need all the information i can get.

[Micah]

Ok so here’s an update for my 1947 model G.... I bought the mag pinion extractor and went ahead and set the timing so that the points just start to open 0.375" before top dead center as recommended. Before I did the adjustment it was set (by the previous owner) so that the points just started to open at TDC at full advance. Now that the timing is right, the revs increase quite a lot when I put the control in advance. Before the adjustment, if I retarded it would cut the motor, this is how I have been stopping the motor up until now, now I the only way I can stop the motor is by putting my hand over the carbs intake. I think this bike is supposed to have a valve lifter for this purpose but mine doesn’t have one. If anyone can explain or post a pic of the lifter it would be much appreciated because I don’t understand how it works nor have I seen one.
So my main question is; are the revs supposed to increase to about double the full retard speed when advanced? I set up my carb before I started tinkering with the timing what’s a good idle speed in full advance and full retard?
I hope this all makes sense. I bought the book “the book of the Royal Enfield” and it has been helpful but I feel like it assumes a little knowledge that I don’t have yet. I’m looking forward to getting her on the road.

-Micah