Contact breaker problems

[peterbateman]

I've been hesitating about asking this, so as not to be showing my ignorance, but pride swallowed, here goes! My 49 NH has been 'well fiddled with', and I'm trying to get the ignition timing at least fair, and not having any luck. I've got all the "books" etc, but they presume that one knows which is 'advance' and 'retard' on the slip ring, which I dont. My "lever" is on the wrong side of the bars, and one fellow told me to pull the cable for advance, and another said the cable should be relaxed for full advance ( which sort of makes more sense, in the event of a cable break ). When I take the little plated cover off the contact breaker, its obvious how the slip ring works, but I cant tell if the "anti", or "clockwise" motion of this ring, is advancing, or retarding the setting. Must be a mental block, and I will be kicking myself when I figure it out.
One more thing; when I tighten the center hex screw, anymore than fingertight, it locks up the slip-ring, making the advance/retard lever stuck anyway. Ive packed it out with a bit of wire, but there must be a better way to get the points breaker tight, without jammin the slip ring?
ps. does anyone know where I can get new parts? Especially the whole assembly, which is well worn.

[pete.collings]

Looking at the contact breaker end of the magneto, if the cable/cam plunger is on the left hand side, then it is slack wire for full advance, if they are on the right hand side, it is tight wire for full advance.
I believe Ariels generally had a tight wire advance setup, I have used a slack wire setup with an all alloy motor, but the cable then rubs against the barrel, and I had to make a spring wire spacer to keep it away from the barrel. The main problem with a tight wire advance is if the handlebar lever slackens, and allows the spring above the cam plunger to slacken the wire and retard the ignition. There are tales of exhaust pipes glowing red as a result of this happening!!

The cam ring tightening up sound like the end of the armature where the contact breaker assembly fits has been shortened, or possibly a pattern block with too long a locating stub has been used. Another possibility is the cam ring itself is a thicker type, amongst my various mag spares I have two different thicknesses of cam ring, and generally the Ariel Magdyno mag uses the thinner type. There are new pattern points block assemblies listed on Ebay from time to time, I believe made in India, priced at what seems to be the going rate for good used original equipment items, which are hard to find. I don't know how good they are, perhaps someone who has got one can advise. The original were of an alloy material, the pattern ones look like brass castings.

[nevhunter]

The originals are diemetal. If the points assembly contacts the cam there may be several causes. There could be too many shims under the rear ball race, or the part may have been filed/altered. The fitting normally bottoms out in the end of the armature as it is not a taper fit. Rudges have pull to retard and the Ariels that run BTH competition magnetos. I think all the others pull to advance where the camplate moves against the direction of rotation of the magneto, when tensioned. Nev

[peterbateman]

Thanks Pete and Nev. Great advice! I shall "pull" the cable, to advance, and maybe give my poor old donc a chance to run properly now. I'd love to be able to replace the whole lot with a modern set-up ( heresy! ) re the make and break circuit, as this clunky old soft metal collection of memorabilia is quaint, rather than efficient. Hell, I may as well just get a Honda! Just kidding. I love the bike, and want a similar year twin now, to keep her company.
Without spending an arm and a leg to replace the whole magdyno system, does anyone know of an aftermarket points assembly, that can be set more accurately? One see's older Ariels than mine, offered for sale with a "Boyer ignition" etc. How is this done?

[Simon.Gardiner]

This is mainly aimed alternatives for twins but there's some mention of 'singles' (albeit BSA, the installation should be similar) in this info from Goffy's web site. (And I've just noticed the kit aimed specifically at Leaders and Arrows !). However, it seems to me that a full replacement ignition kit wouldn't be cheap.
http://www.norbsa02.freeuk.com/goffypazon.htm
There are quite a few other interesting things on the web site too.

[john.nash]

http://www.srmclassicbikes.com/electric ... rsion-kits
http://www.ebay.co.uk/itm/Lucas-Magneto ... 0622916457

To be fair, unless you have a wedge burning a hole in your pocket or buggered magneto that needs a few hundred quid to sort out ....

[nevhunter]

Any alternative ignition system would have no cable adjustment for the ignition timing. While the electronics would have advance built into it, the initial "static" timing has to be very accurate. The cable allows the rider to get it right, ( I am old fashioned here) as you ride along. This is extra effort but is part of the skill of riding older machinery.
The generator part ( especially the drive and regulator) is far more trouble than the Magneto part which can be quite successfully reconditioned and will run for years, without much fuss. (You shouldn't pressure wash your bike, anyhow) Coil ignition requires a battery (which is always flat/broken lead/out of acid/ eaten through the support frame etc). Magneto's forever, They're OK. Nev

[john.whiting]

The maggie jamming up might be due to the paper bearing mount being u/s.Ive seen bearings mounted in masking tape,and insulation tape.If you decide to pull your mag to bits,dont forget the SAFETY GAP SCREW,it must be removed before the armature.Yes I have seen magdyno mags used as points in a coil system,but not since old bikes were worth five quid,registered.Also,dont leave the armature out of the mag,without a keeper,or youll have weak spark.Regards John.

[pete.collings]

There is no safety gap screw in a magdyno magneto, they are found on K2F (and variants) as fitted to Huntmasters. You do however need to remove the earth brush holder and pickup before the armature can be withdrawn, as well as dismantling the dynamo drive assembly. The drive plate can be left in place, and the armature removed by carefully tapping the end of the armature with a soft mallet, preferably with the sprocket nut still in place (but remove nut once plate is free).
It is better to use a keeper to maintain magnetism, although the magnets are supposed to be permanant, and I have used mag bodies to give a good spark when they have been stored without a keeper for some time. I suspect continued overheating of the magnets is a more probable cause of reduced magnetic field intensity.

[nevhunter]

Magneto's lose a bit of magnetism when the armature is removed. If the case is left without a keeper (or armature) in it and banged around for years it will lose a lot more magnetism. The worst thing I find is someone trying to magnetise the magneto and getting the polarity reversed. I do a lot of remagnetizing and find the lucas magnyno's one of the hardest to get a good strong magnet in. This makes the starting spark a bit weaker than desireable sometimes. Nev