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ET: Engine (Twin) Old Coil Ignition Points Identification


Rob H

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Hi all, I have an old coil ignition system on the bike and looking to replace the points but have no idea what they are or where to get some. I am guessing they probably used some readily available car points but what ones? Anyone familiar with this system?IMG_1965.JPGIMG_1969.JPG
 

Rob H

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Any advice on what the points gap should be on these?
 

vin998

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I would suggest 15 thou which is what I use on any coil ignition system with points.
 

Glenliman

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That looks to be the same system as I have on my well used Rapide.
When I bought the bike, the Australian seller , who had owned the bike ten years and ridden it for about 20,000 miles, said " You are going to love the electronic ignition on this bike. 1 kick starting every time."
The second part was true( nearly)
Apparently he had never lifted the points cover.
Things I have learned about this setup-
1. Never use pattern replacement points. Always use original genuine Lucas new old stock points.
2. Lucas points are capable of lasting a very long time. They are not like the old North American automotive points of the 60s/70s.
One set can go for 50,000 miles. I'm working on that!
3. The starting with this setup is ridiculously easy.
4. A points gap of 15 thou will get you ignition on one cylinder only.
That close of a gap ends up robbing the coil for the rear cylinder.
I encountered this problem by accident after removing perfectly good Lucas points then replacing them with Japanese Daichi pattern points.
I started with a 25 thou point gap at home and ended up with about 18 thou and running on one cylinder 400 miles from home. We had the best of the best Vincent experts on hand and they tried very hard to sort it out, but without being familiar with that system- it was decided to haul the bike home as cam timing must have slipped.
The 18 thou gap looked right to anyone familiar with magnetos.
It's not enough for this system.
Next day I more or less discovered this by accident when my truck transport vaporized and I was sitting looking at the bike.
I noticed the gaps were much smaller than I had set them at home, so I opened them up.
It fired right up on two cylinders and ran great most of the way home. 75 miles from home it went back on one so I opened the points a bit and away it went on two again.

After that I tried to corner the market on NOS Lucas points.
I have enough on hand to run for a quarter of a million miles or so!

That's about all I know about it except Ill add that the bike goes like hell, better than it should on paper, maybe that ignition is part of that?
Glen
 
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vibrac

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To the coil ignition ignorant opening the points may do something electrical but it certainly moves the ignition point earlier perhaps resetting that and reverting to 15 thou would have had the same effect and given the system an easier time, but what does a BTH acolyte know?
 

peter holmes

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Know Thy Beast states 12 thou points gap for the Series D Lucas distributor, seems to work fine on my D Comet.
 

roy the mechanic

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Glens story sounds familiar. The points close due to wear on the heel , this can be reduced dramatically by applying a small ammount of h m p grease to the cam. Also as there are two sets of points,I would recomend using two condensers. I could say why, but it would need around 3/4 of an hour to trypewriter it up.
 

vin998

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The standard points gap used by Lucas on any of the coil ignition distributors in the 60's & 70's for bikes and cars was 15 thou with the earlier 12 thou figure a throwback to magnetos. Later on they used to specify dwell angle rather that points gap. If a distributor requires a larger gap then the problem is with the points not operating correctly or a soft heel wearing quickly and so its the replacement points that are the problem and not the gap. The other problem with replacement points is the closing spring can be wrong spec and so the points end up floating which again can be masked by opening the points wider. Also look for badly made cams and cams that can move due to worn distributor & bearings and even a bent shaft in the distributor.

I had a Triumph car years ago with 6 cylinders and one set of points set to 15 thou and one condensor and that car could rev to 6000 rpm and the single condensor worked fine. The recharge time of the condensor is perfectly capable of coping with firing 6 cylinders so two cylinders for our bikes is not a problem. In fact opening up the points gap potentially reduces the time that a condensor has to recharge. The recharge time is all to do with the value of the capacitance of the condensor and the inductance of the ignition coil and can be calculated. Its basic electrical / electronics theory which I used to use at work.

As Tim says, if you alter the points gap you also alter the set ignition timing so opening the points to 25 thou to compensate for a badly wearing heel will cause other problems because as they wear and the points gap closes then the ignition timing will retard itself at the same time and this can be by quite a few degrees.

I have been running a system just like the initial posting on my Rapide for over 25 years and have had no problems running at the specified 15 thou. Like Roy suggests though I run two condensors and two seperate ignition coils and the reason for that is if a coil or condensor fails I can still run on one cylinder and get home.

The solution is to find a decent set of points and decent manufacture condensor which is difficult today as no new vehicles use such an ignition system anymore. Most new condensors/ points today are made in China.

Simon
 

Pete Appleton

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As Simon says, two coils - two condensers - you are effectively running two seperate ignition systems and the only concern with the points gap is to get the dwell, hence the coil charging time right. You can ignore everything below.

If you have two sets of points and only one coil then you have got the points wired in parallel. As per the old Ford V8 Pilot engine. The point gap complication with this comes about because for it to spark you need BOTH sets of points open at the same time.

Consider cylinder 1 firing. This happens when set of points number one opens. If the points are wired in parallel and points number two have already closed, due to a small gap, then opening set number one will not cause a spark because the electrical path is continuous through points two. For cylinder one the chronology goes...

Points 2 still open.... Coil charging via closed points 1
Points 2 still open. Points 1 open to fire the spark.
Points 2 close to begin charging (dwell) period. Points 1 remain open ready for cylinder two firing.

Ford supplied a horrendously complicated angle gauge / test lamp system to set the V8 up. For a twin cylinder engine you should be able to do this visually. For a twin points / singlecoil system the cam needs to be different from just a single cylinder cam with two sets of points on it.

For a 'V' engine one cylinder will be more susceptible to this than the other. You might even need two different gaps. - although that might mess up your 310-410 cylinder timing.
 

vin998

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Well spotted Peter, I had forgot about the cam profile. The system I use (made myself) the cam profile is such that its impossible to have both points closed at the same time so it can be used with the points wired in parallel with one double ended coil or seperately with two condensors / coils etc.

If you have a cam that keeps the points closed for most of the time all that happens is you use more electrical power for no extra gain. Once a coil / condensor is charged up the coil will still conduct DC current which is wasted electrical power if the points stay closed and can potentiall lead to overheating of the coil.

Simon
 

Glenliman

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Simon, you aren't the first to tell me I have the wrong end of the stick re the narrowed points gap causing the problem. :)
My system uses 2 coils and 2 condensers.
It doesn't matter if I fit Lucas points or other points, if the gaps are closed to 15 thou, one cylinder cuts out every time.
So I set the Lucas points at 25 thou , then five years and twenty thousand miles they might have closed up to 23 thou. It's not a high maintenance system!
Anything above 20 thou works on this ignition. Below 20 is where the problems start. That doesn't happen with the Lucas points so long as you adjust them once in a decade or so.
When looking at the system with a multi tester on hand it's easy to see why the narrow points gap robs one cylinder of spark.
Pete explained it above and did a much better job of it than I would.
John McDougall had a look at the ignition when the engine was in at his shop for a top end rebuild not long after buying the bike in 2004.
He was familiar with the system, named it ( I've forgotten the name) and said " You need to run a wide gap with these, around 25 thou"
Yup.

Re the heels wearing- no amount of lube will help the Daichi points. The heel material looks the same as the Lucas, but it isn't the same.
On the other hand a few drops of o on the wicks of the Lucas then forget about them for years and many thousands of miles.
Photo of the OEM Lucas points that work so well on my ignition.
When stockpiling the OEM Lucas points I purchased 2 sets on eBay that were packaged in Lucas boxes just like the one in the photo.
The point sets however were not Lucas. Instead they appeared to be the Daichi items, or copies of those. They did not have a made in England stamp on the plate and there were other differences from the genuine OEM Lucas items.

These look to be the real deal




Glen
 

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stu spalding

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The points cam on my set up gives a 60 deg dwell angle and two twin lead coils draw 6 amps static but this drops to 1 amp when running, this is using MZ TS250 points which are running backwards but don't seem to mind as they originally ran at 5000 rpm on a 2 stroke. Simon advised me that using the points gap to set the timing between the cylinders was fine (within reason) as with both gaps the same there was a 2 degree difference between pots. In one instance the timing between pots was checked after 6,000 miles and was less than half a degree out. I don't think I'll be jumping on the electronic bandwagon just yet. Cheers, Stu.
 

oexing

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I fail to see the drama with contact settings on a mag. A good mag should produce great high tension when spinning, the higher speed the better. And on a twin engine not the least critical , I say. But then the rotating coil Lucas was never really great at that, the later type rotating magnet should be superior for more than one reason.
Now look at this magneto from a 9 cylinder radial engine, one contact breaker, one coil, one capacitor, nine lobes . Max. speed on that engine is 3000 rpm, the crank is the limiter here. This mag will do half inch sparks when spun with fingers only , definitely, and that is my test for finding shot coils there. Dwell angle in a twin magneto should never be that critical, but if actually so, I´d suspect shot bearings and fits in the magneto in various places instead.

Vic

P1030717.JPG


P1030694.JPG
 

oexing

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Well, yes, it is a mainly battery coil ignition thread. But then , a mag IS a coil , contact breaker and capacitor ignition system all the same, just the electric current is generated in the mag. Otherwise the dwell angle is equally important, set by the breaker gap and cam shapes.
Anyway, we are mainly talking about twin ignitions up to max. four cylinder engines , I suppose ? So no question that dwell in a twin is in no way critical and so is the breaker gap. Even six cylinder engines are no drama at all with one coil, one capacitor and one contact breaker - once you stick to published dwell angles and gaps. Millions of car sixes were operated in that way, so I am struggling to find a reason for seeing troubles in a twin. My photo of the nine cylinder mag may show that - when expecting 3000 rpm from it that would be comparable to a 6000 rpm 4 1/2 cylinder engine, so obviously safe enough with one coil and breaker - even more so a twin and its 7000 rpm max .
Again, if you face problems in your ignition it is not your dwell angle or contact gap setting in all likelyhood, really. You´d better wiggle all components and wires in the unit and look for clapped out fits.

Vic
 

Pete Appleton

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It is noticeable that the cam profile on the multi cylinder aero mag is very short and lumpy, thus giving maximum dwell time regardless of point gap.

A typical coil will require 2.5 milliseconds to achieve a reasonable saturation in order to give a decent spark. At 4,000 RPM that equates to 60 degrees of crankshaft movement. With an unknown cam / points setup it is worth checking that this figure is attained, something that I suspect Stu, above, already knows.
A small point gap will increase dwell and, as Simon mentions, will waste electrical power and could overheat the coil. Charging past the saturation point has no advantage.
Talking of charging the condenser in the same context as dwell is not really correct. Dwell is when the points are closed. As one side of the condenser is connected to earth and the other is connected to the points the condenser is discharged during the dwell time. Its main function is to quench the voltage rise as the points open in order to prevent arcing and provide a clean break. The points must be open wide enough by the time that the condenser is charged so that they are then unable to arc. Too small a gap can lead to arcing and will give similar symptoms to a failed condenser.

I agree with Vic that if a reduced points gap, when measured static, is cutting one cylinder out then it is likely to be wear in a component causing the gap to be further reduced when under running conditions.

But hey, if decent points and a 25 thou gap fixes it then who cares?28230
 

Robert Watson

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If I recall on Glen's bike when it had the small gap and running two sets of points on a 50 deg engine (as it was designed for a parallel twin) something about one set of points grounding thru the other when the one of the sets was supposed to be trying to deal with the coil, and that was why it went onto one cyl and why opening the gap to 25 thou let it function as god (and Lucas) intended. Certainly it was nothing to do with worn components!
 

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