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Discussion Starter #1
hey,
novice question here. where on the INTERNET can i find info on how contact breakers work.if that makes sense. i need a place to read and see how they work.i got a manual for my bike but they talk in sense that you already know how it works. just never had a bike with them. are they good? what is a good replacement? just some good reading for knowledge.
i have a 70tr6c with a 71 motor. with a Lucas i think. sorry for the stupidity.
thanks for the help!
:-g :chug:
 

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Don't know about the net try going to the library and look for a book on basic auto electrics. (MOTORS come to mind) Points is points what ever they are in. Also you can try resale/antique shops I have had good luck there for books.
One of the best books I ever found is from about 1920
Haynes has a book out about cycle electrics.
The biggest thing to remember is you bike has a POSITIVE GROUND electrical system not negative like your HD

As an after thought I went to wikipedia.org Try that site for the info you are looking for. Use key words iginition points
or contact breakers and see what comes up

[ This message was edited by: KADUTZ on 2006-11-26 08:18 ]
 

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I highly recommend the Essential Guide to Motorcycle Maintenence by Mark Zimmerman. Its available on Amacon.com. He gives an in depth summary of all the motorcyle systems and components including older ones like points that are not currently being used. He has another book on motorcycle restoration that is good too. Both books have a number of references to Triumphs and older Brit bikes.
It appears he has quite a bit of experience with them.
 

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There is a capacitor that is electrically tied into the wire (circuit) of the points.

The capacitor builds and stores a charge from the alternator and/or battery that is discharged when the points are opened by the rotating cam, timed to fire as the piston approaches top dead center.

When the discharge occurs, it triggers a secondary impulse in the windings of the coils, which causes a spark to jump the gap at the spark plug's electrode.

You are now a professional.
 

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Contact breaker points are simply a mechanically operated switch.You can see how the little cam opens, and closes the points, right? When the points are closed, they complete a circuit through the windings in the coil. The duration the points are closed is called The "dwell time"(some people say"dwell angle" or "dwell interval"it means the same thing). During this dwell time, the hundreds of windings in the coil are being "saturated" with electricity. As long as the points are closed, this current can go to ground through the points.

When the points open,thats when the fun really begins. The circuit is broken, so all that juice has no where to go. Inside the coil, in the center of the windings, is the "pile" The pile is grounded through the plug wire, and ultimately through the sparkplug. All that swirling eletricity jumps from the windings to the pile all at once, greatly amplifing the current, and ZAP! You get a nice, fat, blue spark at the plugs. This is, by the way, the same way the coil works on your Sportster, and your car, and anything else with an ignition coil. It's just that on those, the circuit is broken by a transistor, instead of a mechanical switch.

There is another little doohickey in this system called the"condenser" or "capacitor". It looks like a little battery with a wire sticking out one end,and in essense,that's what it is . It has the "capacity" to store a small charge of electricity. Its purpose is to bleed off the excess current when the points open,to keep "arcing" to a minimum.
If there is too much arcing at the points, they will weld themselves together, in the same way an "arc" welder works.
Condenser failure is the major cause of point failure.

The next part you may not be familiar with is the "centrifugal advance" All internal combution engines have some mechanism to advance, and retard, the spark timing. In the old days we did it with a little lever on the bars. New engines do it with a computer, and all kinds of sensors(shudder). If you reach in and grab the point cam, you will find you can twist it back and forth.If you take off the point plate you can see how it works. Those little spring loaded bob-weights swing out, due to centrifugal
force,as the rpms increase,causing the point cam to twist, and advance the point at which the points open. Thus advancing the spark timing. All British bikes that I have ever worked on(with points) have the timing set at full advance, 28 to 30 degrees before top dead center. We don't worry about base timing.

It's this little advance unit that causes otherwise reasonable men to abandon our wonderful,reliable, and time proven points,and condenser ignition system in favor of some %#*@&% black box set-up, that surely will leave them pushing. You see, if that advance sticks retarded, the bike will not accelerate, and will overheat, and be generally unrideable. And if it sticks advanced,well all those stories about the kickstarter kicking back, and breaking legs? This is where they came from!

Is it reliable? Yes, but it must be properly maintained. The points themselves give little trouble, other than the rubbing block eventually wearing down. Also inspect the contacts for pitting, or burning. They must be kept free of contamination from water, oil, or other fluids. You can get contact cleaner aerosol, at the auto parts store, for this purpose. The condensers will eventually just quit working, causing the points to burn. Also the little wire likes to break internally, and you don't notice it untill you tug on it. If in doubt, replace. The advance must slide snugly over its shaft, with no wobbling, yet must twist freely, with no binding. also the bobwieght springs break, or lose tension. If in doubt, replace.

Sorry to ramble on so, but you asked for it. Amazing this drink called coffee!

:-g
 

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Discussion Starter #6
hey CommandoRdster
thanks man that is the best explanation Ive gotten. I'm not a pro now but the gist of it now. ill check all that you said and look at all the parts that you mentioned. i got a spark but it weak. I'm thinking of getting a ARD magneto. Ive heard from so good guys that its the*****. but for now ill work on getting my points system to work
thanks again guys for all your help.
 

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Thanks for the kind words. I don't know anything about the ARD mag, but I'll bet there are a hundred other guys on this forum that do. Why don't you start a new thread "ARD mag opinions" or something like that? The only streetbike I ever had(read carefully:
HAD!) was a '67 XLCH Sportster, and that thing was a M*****F*****r to start. I guess the newer mags have a little spring loaded thing, that winds up,then releases, for a hotter cranking spark.

BTW Paul, I checked out your website. Man, I wish my stable looked half as sweet as yours!
 

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Great 'splaination of the points system.
Small addition....the points surfaces must be clean and oil-free, since they are switch contacts and must freely pass current when the points are closed. If they get "burned" , oxidized, or contaminated with oil, they will not function properly.
Condenser failure is almost always an "open circuit" and this allows the current to arc over between the contact faces as the points open, delaying the breaking of the current, which retards the spark and makes the cylinder run hot and sluggish.

[ This message was edited by: Mecchanica on 2006-11-30 14:53 ]
 

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dgfironworks,

I'm putting together a "paper" dealing with the electrics on Meridens - how they work and how to fault find. Just finished the ignition section - including Boyers. Are you interested in having a read, and perhaps providing some feedback on readability, ease of use, etc?
If so, send me your email address by PM, and I'll mail you a MSWord copy.

Pete
 

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I'm interested in reading anything that might explain why the left side refused to run smoothly and fouls plugs I have replaced everything more than once and am now thinking another coil. . Carbs have been tuned and re jetted Timing has been set but still intermitent firing and black carbon plug. I'm ready to try the boyer. Does this eliminate the coils? can I use the 12 v bat. ? Anthing else I need to know about timing it after it's insalled ?
 

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Boyer still uses coils, but usually two 6v coils in series. If you are oil fouling the plug, you will get intermittent running and stalling. Smell the left plug after you pull it out. Do you smell fuel? Is the fouling oily? If it smells of fuel, you could have a carb float level problem. If oily, rings or guides (or both) need renewing.
 

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good explanations, but let me try to put it in layman's terms.

the coil has 2 windings..a primary (points circuit) and a secondary(spark plug lead).

when the points close it collapses the magnetic field and the secondary fires the plug.

the condenser acts like an electrical shock absorber...purpose is to momentarily absorb the electricity as the points just open and close...that is to keep the arc off the points.

the problems with mechanical points are
1. the fiber that follows the cam wears down and the points lose their gap and don't open any more...hense no spark
2. the little wire can wear thru and ground thus no spark
3. the condenser goes bad and the arc dirties up the contact surface...and the electric won't travel thru the crud...no spark
4. oil seeping thru the seal can contaminate the contact surface and crud it up...hense no spark

to troubleshoot points, you should have a continuity tester to determine when and if they are making contact.

you can dress the contact surface with fine (like 600-1000 grit) wet or dry sandpaper as long as you don't get thru the silver, and shape them both convex...reason is you want one point of contact.

if the coil is powered off a battery (rather than magneto) you can turn the key on, and ground the points wire and you'll see the coil fire the spark plug (grounded to the head).

you want a strong blue spark...an orange spark may be a weak coil...no spark...see above.

the beauty with points over modern stuff is if modern stuff fails you're calling for a tow and parts...if points fail 95% of the time you can fix it and limp back home...unless the points arm breaks.

us old guys did very well with points...tho there is something to be said for modern. points take more mantainence.

if you have no spark...points is the first place to look. if they make and break OK (with the continuity tester), then you have to troubleshoot the hot wire to determine the coil is powered...if so...then check out the secondary for broken wire or faulty plug or connector.

you can look at the contact surface to tell whether the condensor is over or under rating by seeing where the arc direction is built up.

both points and spark plugs can be cleaned up and used far beyond life expectancy.

If I were going ATW on a bike, finding myself way out in the bush far from help surrounded by cannibals, I'd personally prefer points with a couple spares on board.
 

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On 2006-12-09 16:08, psds wrote:
I'm interested in reading anything that might explain why the left side refused to run smoothly and fouls plugs I have replaced everything more than once and am now thinking another coil. . Carbs have been tuned and re jetted Timing has been set but still intermitent firing and black carbon plug. I'm ready to try the boyer. Does this eliminate the coils? can I use the 12 v bat. ? Anthing else I need to know about timing it after it's insalled ?
low compression can do that.
a broken ring, bent valve, broken spring, carbon under the seat.

do a compression test. sides should be within 10-15% of each other at the max.

reverse the electrics side to side and see if the problem follows

fouling can also be retarded timing...or one cylinder leading the other. did you sync the throttle vacuums?

hotter plugs?

run out to Sears and get one of those spark testers that look like a pocket pen...you put it against the wire and it will show spark without pulling a plug. if it has an intermittent miss you'll see it.

also, a plug that fires in atmosphere may not act the same under compression.
 

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psds

I have the same problem with the left plug fouling first and the left exhaust pipe looks like the left cylinder is running richer. I have adjusted, switched, and checked everything there is to adjust, switch and check. I have been wondering if using the side stand all the time has something to do with it. Oil going to the left side of the head when parking?
 

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On the OIF engines, there is oil surging back and forth throught the left main bearing due to the engine's breathing through that bearing. Some is picked up by the chop and flung into the cylinder. Not so with the earlier timed breather engines, through 1969.
 

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you may find these links useful

http://users.mrbean.net.au/~rover/ketterin.htm
http://www.jetav8r.com/Vision/Ignition/CDI.html

you have the basis of a very good bike, treat it sensibly and it could give you another 40 years of fun. I had a 1970 TR6, and it was the best bike I ever had... as I progressed up through the ranks of triumphs offerings, they got better..
good luck.. When in doubt sit on your hands, If that dosen't cure it, go for a cuppa or pint.
 
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