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Atlas distributor leads which way round?

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Sorry for the dumb question; my Haynes manual says the rearmost lead goes to the left cylinder. My distributor is located in such a way that the 2 ht lead outlets are almost vertical. The lower one is very marginally more rearward by a centimetre. So is this lower one to go to the left plug? Cheers everyone.

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Atlas Motors don't normally come with a distributor.  Usually a magneto or points unit behind the engine powering coils.However all things are possible in our world. The simple way to determine which is which, remove both plugs ,using a finger/thumb  feel which cylinder is coming up to compression when you slowly turn the motor over ,with the dissy cap off the rotor arm will be coming round to point to the alloy terminal of the correct lead.  That's assuming you DO have a dissy fitted!.

Thanks Robert. Yes, it’s a ‘68 model so has a Lucas distributor, single coil set up. I had it running a few years ago. Trying to get it on the road again. Great spark and fuel so checking all the other possibilities! Timing next.

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Have you really got a distributor on your Atlas.  The early ones had a magneto and the late ones had a twin contact breaker and advance unit fitted to where the mag used to fit.  These later models had a pair of coils mounted in the space between the oil tank and the battery box.  The distributor was generally only fitted the coil ignition 88 and 99 models that had a single 6V coil, hence the need for a distributor.  It will depend on which cylinder was ready on compression when the points were timed.  So remove the cap and have a look at their position when say the left-hand cylinder is on the firing stroke i.e. both valves closed.  Slowly turn the engine over with the back wheel and 4th gear selected then if you see the points breaking look at the position of the rotor arm.  Whichever lead corresponds to that position will go to the firing cylinder i.e. left if that's the one on compession.  Good luck, Howard   

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Whilst I was writing some more info was added.  In 1968 all the Atlas models had a twin coil, twin contact breaker 12V ignition system with  capacitor fitted to enable running with a low or missing battery.  The 6V single coil system with the 6CA distributor is vastly different to that.  Best of luck with that.  Howard

Exactly that, just try it, if it doesn't work swap it over. I never knew of a Dizzy on an Atlas either. In fact Lucas didn't make such things after 1960ish. I suppose some-clever soul could have found the 18D2 bits and the timing sprocket for the parallel shaft. While delving into this area, can anyone confirm the drive for the twin contact breaker 'gubbins' use on the Mercury, and first Commandos and the Atlas, was it a parallel shaft or did it have the magneto taper. (The latter could allow one to fit a double advance retard if so! Not a nice idea!)

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Hello Al - I can confirm that my Mercury has a parallel shaft supported in a ball bearing and the drive sprocket attaches to the shaft with a roll pin.  The advance unit attaches to the parallel shaft on an internal taper under the contact breakers and is secured by a 1/4 inch UNF bolt.  

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I have seen an Atlas with a distributor, No reason not to fit one.  Probably less unreliable than the cheap and nasty,  but correct points unit.The only advantage of the points unit was its ease of fitment of a Boyer.  I have both systems on bikes and I prefer the dissy. No kickback with a flat battery, a decent amount of advance at 2500 rpm , Ability to "tune up" the timing at the roadside,No use for a strobe .All easily understood by old fossil.

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Robert  "No kickback with a flat battery"  you say........ from my experiences with the 18D2 distributor  - flat battery = no spark at all.   Unless of course you've wired it up with batteryless trials type alternator or the Emergency Ignition Switch from a Coil 99.   Surely none of the Atlas family were 6V so you must have made major changes to the electrics ?   Regards,  Ride Safe, Howard

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Hi Howard, My 99 has 12v system uprated lights  and a Commando hi output alt and zener. It also has a 2mc cap so it will start and run with a flat or no battery, The dissy is helped by a Boyer ign booster which means the points capacitor is redundant and I get a really powerfull spark. The points now do so little they do not wearout. The bike also has indicators and a 12v aux socket that powers a sat nav, phone or camping light .It also has an on board compressor for tyres ,heated grips and a power jack for my radio controlled heated jacket .I'm fitting an electronic automatic chain oiler at present. Wondering if the compressed air horns will fit somewhere. I'm sure the Givi screen will make life a bit more comfy.Its all good! Mr Gadget. PS, do you think a smoke detector advisable?.

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Sounds like all it needs is an electronic sunroof and a microwave oven.  Who needs a Camper Wagen ?  I thought you must have changed things a little.......but hey  !!  Methinks that some punters using 18D2 distributors will not be so satisfied.   Cheers, Howard

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I think you are a bit over the top with the sunroof ,but I can see merit in a microwave, I will probably settle for an imersion  12v element for tea breaks. An inverta could provide 110 v for shaver and toothbrush charging.

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Hello The  Norton Atlas was  never  issued with a  Distributor  They were fitted with the Lucas K2FC magneto  or the twin points modual  and 12 volt for later machiens    so if your ignition lead,s are vertical  then the bottom lead gose to the left hand cylinder and the top one goes to the right hand cylinder  OK  Yours  Anna J

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In theory, the rear magneto lead goes onto the left plug.  But if yours turns out to fire on the wrong stroke, would you take off the primary and timing cover, set a timing disc, and redo the whole timing, or just swap the plug leads over? 

On my Dominator, I actually don't know which mag pickup fires which cylinder, and am not aware that it makes any difference.  It matters that you have a strong spark and that it arrives at the right time

Paul

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If you get it the wrong way round there is not normally any problem , you may get a spitback   as the spark occurs at the end of the exhaust stroke and beginning of inlet,but at that point there is not much in the cylinder unless the motor is well flooded with tickled fuel.

There is an anomaly here Robert-a Commando High Output alternator would fail a single Zener Diode (too much power) that is why the Commando MKIII had twin Zeners. Also I have always under stood that the ONLY alternator that will start without a battery is the common or garden RM21. SO can you please clarify above, does the bike really kick start without the battery? What alternator do you have? This point will be a problem as the stators never have any numbers on them, you would have to do a full output test and measure the 12Amps at DC.@7000rpm.If you have got a single Zener then of course you have the usual RM21. Please let us know?

Smoke detector?-of course, but don't all Nortons smoke, so no case to answer.

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The alternator is a Commando ES one so high output for a Dommy but normal for a ES bike. Yes the bike will start without a battery, I found this out when it was still fitted with the original  uncapsulated 1959 alternator switched to 12v and a 2mc. I took the battery off for service and forgot. A week later and a few miles up the road I noticed  the ampmeter behaving oddly and the penny dropped .I returned home at reduced pace wondering about repercussions,but all was well,at least for a few years. I run with lights on, keep off motorways and have a biggish battery under the DL panels (along with an unforgivable mess of spaghetti wiring!). I have a new rectifier waiting in the wings but am too busy fixing family and friends bikes, so the Zener will have to tough it out for a bit.The up to 70 watt heated jacket can be adjusted(on the move) to keep things in a sensible area.The component that seems stressed is the encapsulated rectifier (with  16sq inch ally heatsink fitted) . I carry a spare. Will it start with a flat battery?, Don't suppose I will ever know.

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Those uncapsulated alternators was one of the reasons why Mr. Lucas is said to have invented darkness. But it was not easy to make electrics for motorcycles then. Vibration, damp and oil is not friendly to the electric system. Add to that, the rudimentary knowledge of electricity most motorcyklists had. Traces still seen when trying figure out the spagetti mess of cables that previous owners have fitted.

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Hi Mikael, I must have been lucky with my early Alt as it lasted 58 years the last 20 years on 12v. ,the rotor never gave any problem and still is very magnetic.  I can't blame previous owners for the spaghetti as the majority of the loom is original with only my "improvements".All concealed behind those usefull DL panels.

 

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