Spark plug failures - 1967 Atlas

Malcolm, Chris is correct in that this sort of thing has been discussed before. But what strikes me are two things: 1) Why on earth are you mot using Champion plugs? I have never had one fail in 40 years of motorcycling. (Others may of course beg to differ) My 650 uses N4c plugs. Atlas maybe N4c or N3c but you can check that out as to what is recommended..

2) You have changed from Magneto to electronic ignition. Did you change your HT leads from the copper core type to the fiber type?

Can't see anything else on here to cause your plug problems, other than dodgy plugs or wrong reach of course.

Good Luck.

Having owned three Atlas bikes I can add a little to this thread. Whether my points are relevant to your situation is open to debate. Two of my 750s had electronic ignition the other a magneto.

I note that you mention flat top pistons. These are usually the Commando 8.9 to 1 compression type which are fine for the Atlas motor with a Pazon spark set-up and 32* of ignition advance. With a magneto and mechanical auto-advance you must run the ignition at 28*BTDC.

I always used NGK plugs with my electronic ignition and it worked fine. The magneto preferred Champion plugs. What is very important are the type of leads from the coil to the plugs, the plugs themselves and the plug caps. The issue that can arise is the plug leads, caps and plugs themselves are sometimes manufactured with a built-in resistance (suppression) and this has to be correct for the coil output otherwise there will be problems.

As Chris G mentions.....there are other threads around this site with more info about this. I am intrigued by your Commando camshaft. The very first Commandos bascially had an Atlas engine so is it from one of these or has it been remanufactured to fit?

Interesting camshaft. Very much like as used in a later Commando engine. How does the engine breathe?

I forgot to mention that I put Commando heads on 2 of my Atlas's and never knew which plugs would be best to use. Champion N3 or N7Y? The N7Y is clearly longer and must put the spark almost in the centre of the combustion chamber. Also the original Atlas had concave, low compression pistons which probably suited N3 or N4 plugs plus the more advanced ignition timing. But what about with HC flat top piston inside? The answer is out there somewhere.....Cue the X-Files music.

Certainly try different makes of plug. In my experience, the Atlas engine isn't that fussy about plugs. Mine has flat topped Commando pistons and magneto ignition and has had NGK B7ES plugs for as long as I can remember - over 20 years and no problems. Anna will recommend Bosch. Try them - it just might work for you.Are the spark plugs sooting up or cracking the insulation or tracking? Do they work on another bike?

Previously malcolm_parker wrote:

Previously Gordon Johnston wrote:

Certainly try different makes of plug. In my experience, the Atlas engine isn't that fussy about plugs. Mine has flat topped Commando pistons and magneto ignition and has had NGK B7ES plugs for as long as I can remember - over 20 years and no problems. Anna will recommend Bosch. Try them - it just might work for you.Are the spark plugs sooting up or cracking the insulation or tracking? Do they work on another bike?

Not sooting up. Not sure whether they are cracking the insulation - no visible sign. Not sure either about tracking. Good point about another bike. I guess I could get them tested?

Thanks.

well Malcolm I ask myself why have you not come and seen me about this problem as I suppose to be the Branch Technical Adviser , Now for a start of you have the Wrong camshaft the camshaft you should have is part number 22729 witch is the same camshaft in my manxman and what happened to the Magneto as there better than any electric ignition you can buy , I rebuild and Test Magnetos and dynamos , I rebuilt my own Lucas KF2C that sitting on my manxman and it was tested too the extreme in 2008 in the worst storm we had yet as I was out on my Manxman coming down the M62 from Kingston Upon Hull at speeds of 80 mph and steam coming of the barrels its was a water cooled engine that day !! and near drowned just trying to put the bike way in the workshop we have only later on we heard of a young guy who lost his life in a storm drain in Hull his foot trapped in a steel fence someone had thrown in there , , and As for spark plugs I been using Bosch W7DTC as advised by Tim Green of Green spark-plug .co these ones are for magneto use, So electronic ignition system will be a different plug number I take a look and find the plug you need , but really you need a Magneto my bike starts easy and ticks over like a watch and runs like a Singer sowing machine , So talk to me Malcolm , I do not bite, yours Anna J

Hi Anna, I thought it was 2007 that guy got stuck in a drain? 2008 was too cold to be out on a bike half the time as 2007 was too wet.

The difference between electronic ignition and a mag is the battery.

Add a Boyer power box and if the battery fails it is still game on!

This may have no bearing on your problem whatsoever, but thought it worth mentioning. I know of two Commandoâs that are fitted with dual output coils, the type with one lead coming out of each end, & both suffer one plug failing, itâs always the same cylinder, or to be more accurate, itâs always the same end of the coil, ie the problem moves if we swap plug leads around. I also know a chap that used to race Citroen 2CVâs, which have a similar ignition coil set up & he used to swap plugs from one cylinder to the other, he maintained if he didnât do this one plug would fail regularly under race conditions, think it was always the r/h one, but by swapping them around between races, they would both last a similar amount of time. He maintained that, due to the design & internal wiring of the coil, one lead had a stronger spark to the other & this had an effect on the plugs, one would burn nice & clean, the other would build up deposits up in the core, by swapping them arround, it evened things up & kept both plugs clean.

Regards, Tim

Very interesting Tim, I have this set up on my 650ss with no issues so far but then it has only covered 132 miles, due to the rebuilt (Not by me) engine being knackered.

I was thinking of getting another of these twin coils for the 99 (With a Boyer Power box in line of course) but now might go for the other option. Could it be an earlier batch with a fault now fixed?

Previously neil_wyatt wrote:

Hi Anna, I thought it was 2007 that guy got stuck in a drain? 2008 was too cold to be out on a bike half the time as 2007 was too wet.

The difference between electronic ignition and a mag is the battery.

Add a Boyer power box and if the battery fails it is still game on!

well Neil it could of be 2007 I know this its was the heaviest rain fail I ever seen in 60 years of my life, my roof was like a water fall it was completely missing the gutter and going straight over the top, we have a 250 space car park and it was under 5 inches of rain water I was padding in it to put the bike way, and near drown doing it, I was soaked to the skin, boots full of water but drying my bike came first, then it was my turn, in the shower, and then dryed off, and fresh cloths on, and how dose a boyer work without a battery, yours anna j

Previously neil_wyatt wrote:

Malcolm, Chris is correct in that this sort of thing has been discussed before. But what strikes me are two things: 1) Why on earth are you mot using Champion plugs? I have never had one fail in 40 years of motorcycling. (Others may of course beg to differ) My 650 uses N4c plugs. Atlas maybe N4c or N3c but you can check that out as to what is recommended..

2) You have changed from Magneto to electronic ignition. Did you change your HT leads from the copper core type to the fiber type?

Can't see anything else on here to cause your plug problems, other than dodgy plugs or wrong reach of course.

Good Luck.

Neil for a 650ss Champion N4 or Bosch W8DTC with Twin carbs , but a Single Carburettor you need champion N5 or Bosch W7DTC

I now run my Manxman on a single Carburettor as in our days with the traffic as it is now, there not much uses for twin Carburettors any more, your better of with a single carburettor as there less hassle and you save on the jungle juice too ,and as for plugs burning out or failing to spark this is down one of two things a condenser failed or a coil failed or both or a over load from some where, in the electrics but the real puzzle too me is why did Malcolm take off the lucus magneto in the first place . only to end up with even more trouble, yours anna j dixon

And yes I find that after 3 years of using Bosch W7DTC I had no trouble in starting hot or cold , and its even better on fuel too, and I have a box full of failed NGK and Nippon Denser Spark plugs As trophy's , most came out of my car, I tried NKG in my bike it just does not like them , and Champion are not bad ,but Bosch are a lot better than any of them, I not even had to take any plugs out yet , in the last 3 years , with NKG or Champion I was taking plugs out every two weeks, well these are my experiences and every one different so that what make the world go round, yours Anna J Dixon

Hello Anna, you might be right about the Champion N5 plug in the single carb 650? The N4, as per book appears to be working fine though, up to taking it off the road.

The Boyerpower box has a capacitor in it and allows you to start the motor if the battery has failed or producing less than 12V and also if the main fuse has blown. You know if you are on the Boyer because your ammetershows no reading. You do however need your charging system to be working or you won't get far. And yes, the set up does work...

Drier weather tomorrow, time to get a bike out.

Previously neil_wyatt wrote:

Hello Anna, you might be right about the Champion N5 plug in the single carb 650? The N4, as per book appears to be working fine though, up to taking it off the road.

The Boyerpower box has a capacitor in it and allows you to start the motor if the battery has failed or producing less than 12V and also if the main fuse has blown. You know if you are on the Boyer because your ammetershows no reading. You do however need your charging system to be working or you won't get far. And yes, the set up does work...

Drier weather tomorrow, time to get a bike out.

Neil Might be right!! I know I am right, and the Better plugs are Bosch W7DTC and I right about this as well, , But your Electronic ignition system Its Not Self generating Like a Lucas KF2C , Lucas was tested to 8000 rpm and the spark then is a constant arc yours anna j

Right Anna, the mag wins during daylight hours if the charging system fails.

I got home from the coast in the dark on my poor man's Manx, with a dead battery, thanks to the Boyer power box having the charge to get started. If the Lucas Alternator had failed too it would have been game up.

Actually I could have left it like that but nice to know there is a back up.

As far as K2F's are concerned: What's the real difference between mags with clip on pick ups and screw on? Competition use I suspect?

Previously neil_wyatt wrote:

Right Anna, the mag wins during daylight hours if the charging system fails.

I got home from the coast in the dark on my poor man's Manx, with a dead battery, thanks to the Boyer power box having the charge to get started. If the Lucas Alternator had failed too it would have been game up.

Actually I could have left it like that but nice to know there is a back up.

As far as K2F's are concerned: What's the real difference between mags with clip on pick ups and screw on? Competition use I suspect?

Well Neil the difference is K2FC is for Competition use so there made with the very best part and there tested to destruction , and there pick ups are sealed so no water gets in and there reliable , too that why at Norvil there going on sale at £780 rebuilt . I rebuilt my own , in 2006 and as not missed a beat since , even in the worst wet weather we ever seen in 2008 the day a air cooled engine became a water cooled engine with all that rain hitting it, and it was turning to steam as I was riding at speed on the M62, one steaming Norton flying down m62 with one very wet rider me, , yours anna J Dixon

Note Bosch Spark plug's have been the most reliable spark plugs since 1901 and there still manufacturing spark plugs today . where as some British manufactures have come and gone, along time ago, so they beat the American/Japanese company NGK by along shot,

yours anna j

2007, the year you got wet Anna.

Thanks for the mag info. If I ever need one rebuilding I'll ask you!

Previously neil_wyatt wrote:

2007, the year you got wet Anna.

Thanks for the mag info. If I ever need one rebuilding I'll ask you!

wet you call it I was near drowned on my bike mate , and I was not the only one ether there was a lot more court out in it too, but they where pushing there bikes not riding them , as the modern electronics got a bit wet, and any thing electroic does not like heavy rain water getting in , that when things go bang, and fuses blow, , But your old fashoined Lucas K2FC went though it all, with no trouble, not even a missed beat.and I was doing 80 plus Mph in all this heavy rain on the M62. well fun and games , yours Anna J

Plug failures are invairiably down to shorting out from contamination . I am old enough to remember taking my plugs into the local garage for sandblasting and testing, My BSA had a plug that i dismantled to clean.Resistor plugs or leads are fitted to suppress interferance to Radio and TV and are needed on some systems for other reasons .The center electrode can be fractured internally (from new!) and can give continuity problems eventually.Regular failure is often down to a combination of contamination and low voltage. Loose plugs can overheat .Contact with a piston is not helpfull. I used to avoid resistors with mag ignition. Stan Dibden should be writing this.

Plug failures are invairiably down to shorting out from contamination . I am old enough to remember taking my plugs into the local garage for sandblasting and testing, My BSA had a plug that i dismantled to clean.Resistor plugs or leads are fitted to suppress interferance to Radio and TV and are needed on some systems for other reasons .The center electrode can be fractured internally (from new!) and can give continuity problems eventually.Regular failure is often down to a combination of contamination and low voltage. Loose plugs can overheat .Contact with a piston is not helpfull. I used to avoid resistors with mag ignition. Stan Dibden should be writing this.

Hi All,

I will just throw this out and see if anyone has any comments.

As far as I know, dual output coils have one coil wound in one direction and the other in the other direction. The result of this is that the spark from one coil will leap from the middle electrode to the end electrode of the plug and on the other plug the spark will go the other way.

Have you ever wondered why 'standard' coils have SW and CB written on them. They will work whichever way round they are wired but if wired the wrong way round the spark will leap the wrong way.

So what does it matter if the spark goes the wrong way ?

One reason is that the spark will always start off on an edge or corner or point, so plugs like the iridium ones have a needle point central electrode to get a good concentrated spark.

If the spark goes the wrong way there is less defined edge so you may get multiple small sparks rather than one good one.

Secondly, whenever a spark leaps from one electrode to another it takes a (very) small amount of metal with it. This is why the central electrode is very hard but the end electrode is soft. Iridium electrodes are incredibly hard which is why they can be a needle point. If the spark is going the wrong way you will get a lot of wear on the outer electrode and a buildup on the inner.

My guess is that if everything is not perfect then a weaker spark due to the spark going the wrong way will cause a miss fire.

If simply unplugging the HT leads from the plugs and swapping them over left to right (both cylinders fire together on electronic ignition) and the miss fire moves to the other side then this may be the problem.

If this IS the case then go back to a pair of traditional coils.

All comments gratefully received.

Regards

Tony

Hi Tony,

That pretty much concurs with my 2CV racing friends theory & also I seem to remember in a conversation on the subject with Al 'the electrics' Oz, he had a similar view. I've never looked that deeply into the way double ended coils work & have no first hand experience of them beyond trying to make sense of & offer assistance to the two Commando's mentioned earlier, but certainly if you wire a traditional coil the wrong way, then the spark does jump from the end (earth) electrode to the core electrode, resulting in noticeable wear to the earth electrode. This is something that often gets overlooked when changing the polarity of a vehicle from + earth to - earth. Later coils tend to be marked + & - but with the older ones marked SW & CB, you need to know what polarity it was designed for to be sure it's wired correctly.

All of my twins are fitted with two traditional coils regardless of the ignition system fitted, (with the exception of my Dommie, which has an 18D2 ditributor so only one coil) & they have always proved to be extremely reliable, but I would hope that if I did have a coil pack up, at least I may be able to limp home on the other. With one double ended coil, I would probably be pushing.

Regards, Tim