Hitchcocks Forum

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Guys... I'm not sure if the 'newbie' is coming with it's original instruction book or not.



I never had a Redditch RE, and my new 1959 Meteor Minor seems to come with a manual advance retard for the ignition?



How and when do I use this, and what is the method of staring engine from cold and warm please?



Any other things I should know so that I don't unknowingly cause it grief?



Thanks all!



















Tabellarius de verbis ostensor gaudium

This is about a BSA M20 but applies to all manual advance/retard engines.

Ignition timing

Ignition timing. Principles and setting.
Correct setting of the ignition timing is one of the key factors in achieving reliable starting and efficient running on any motorcycle. A firm grasp of the principles involved and the reasons for the various settings can be helpful in diagnosing problems and carrying out adjustments.

Basic principles
Some confusion can arise from the terminology used relating to ignition timing so the following is a brief guide to the basics. When the spark occurs and the fuel air mixture is ignited the resulting ‘explosion’ drives the piston down the cylinder and the force of the explosion is transmitted to the crank to produce rotary motion. To produce the maximum effect the piston must be just past the top of the compression stroke as the explosion reaches its full potential. (and thus correctly positioned to be driven down the cylinder). It is to achieve this state that the spark is ‘timed’ so that the maximum force is exerted when the piston is in the correct position.
The explosion itself takes a small, but measurable amount of time to reach its full potential after the spark occurs. Due to this slight delay in the explosion reaching its full potential the spark is delivered slightly before, or in ‘ADVANCE’ of the piston reaching the optimum position for power transmission. At engine speeds over about 1000 rpm, despite the variation in piston speeds, this time delay is treated as constant for machines fitted with a manually operated advance and retard, and in the case of the BSA M20 a figure of 7/16” before top dead centre (before the top of the compression stroke) produces the desired result…with the explosion reaching its maximum potential as the piston arrives in the optimum position.

So, if the spark is incorrectly set in relation to the piston position and is occurring too early it is too ‘ADVANCED’ and if it is occurring too late it is too ‘RETARDED’. There is also another factor to take into account and that relates to the manually operated advance and retard facility provided. When the spark ignites the mixture the time taken for the explosion to reach its full potential is basically constant at all engine speeds. However, at slow engine revs (under about 1000rpm) the piston is moving far more slowly than it would be at say 5000rpm. Consequently although the explosion time is constant, the time taken for the slow moving piston to reach the ‘optimum’ position is longer and it effectively arrives at the correct position after the explosion has reached its full potential. The manual advance and retard lever provides the solution to this ‘slow speed’ problem. Using the lever the spark can be ‘RETARDED’ ,or made to occur later, allowing the piston the time to arrive at the optimum position. This is the reason why the ‘RETARD’ facility is only ever used at low engine speeds, to aid starting and whilst making slow running adjustments.

(I would add to that "flogging" up a long gradient is another time retard the spark.)

Thanks Papasmurf



so retard it for starting and maybe if in 4th at slow engine speed as you say, long uphill. I guess trial and error for the slow running bit.



My New bike comes Friday. The cheshire cat couldn't hope to come anywhere near my smile at the moment!

Hi Scaly, I hope you cut out and posted the form at the bottom right of the ad you have shown, to get details of the hire purchase plan for your new machine ! Cheers, Paul.

I thought about it BW, but everything was in guineas, and I thought they were those large hamsters?

One of my old BSAs had an adjustable steering damper I don't know if it is the same for the Enfield

Advance/retard lever?, strange afaik all the meteor minors had coil ignition.

As you say Scaly, retard for starting, advanced for just about everything else. Congratulations, you've chosen a lovely bike.

It has something that looks like an advance/retard lever. Will know Friday.



Thanks all, The bike is named, see separate post "What's in a name"

"old" handlebar mounted advance/retard levers and choke levers are more or less the same.