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Old 09-30-2009, 07:54 PM   #1
mitchberry
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Default motorcycle condenser questions.....

wiki answers has this to say about condensers...

It is basically a temporary storage device for electricity. The condenser is a simple capacitor that can store a small amount of current. When the points begin to open, the current flowing through the points looks for an alternative path to ground. If the condenser were not there, it would try to jump across the gap of the points as they begin to open. If this were allowed to happen, the points would quickly burn up and you would hear heavy static on the car radio. To prevent this, the condenser acts like a path to ground. It really is not, but by the time the condenser is saturated, the points are too far apart for the small amount of voltage to jump across the wide point gap. Since the arcing across the opening points is eliminated, the points last longer and there is no static on the radio from point arcing.

SO......... that means that there ISN'T supposed to be an arc across the points when they open?????????? i kind of thought there was....

i guess i DO need new condensers.... ****it
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Old 09-30-2009, 08:46 PM   #2
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There will always be a little arcing. When the points open, the collapsing magnetic field in the coil creates both about a 10,000 volt spark on the secondary side (tot he sparkplug) and nearly 300 Volts on the primary side (the side that is usually 12 Volts). The capacitor absorbs this 300 volt spike as the points open. The 12 volt supply from the battery is not absorbed by the capacitor, so there is a little 12 volt arc, rather than a 300 volt arc.
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Old 09-30-2009, 09:31 PM   #3
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in my case it's a 6v bike.....
but aside from that,

basically this means that the point that has less spark has a condenser that is working better than the one that has more park? Sometimes there's a rather bright spark here n there on one of the points, there are infrequent misfires it run's rough etc... the timing is set to the best of my ability though... and i have lots of weird electrical problems tht i've posted a lot about the last few weeks..

I guess really on a 40 year old bike that hasn't been started / run or driven sice 1973, it would probably be a good idea to change the condensors out anyway, but, i just put a less used alternator system on it which had what i assumed were good condensers on the bike... (and did buttloads of other things too....)

it went from being parked for 36 years to able to be taken up and down the street but not dependably in a matter of about a little more than a month! I'm trying to get it to be dependable so i can at LEAST ride it to the store without the worry of having to push it a few miles back home because either the battery has died or it won't start, or it gets flooded or whatever. But, there's no sense in driving my 17mpg '02 camaro 2 miles to the store and back for sodas you know? (in fairness most camaros get better mileage than that. but mine runs a little over 500 horses. I should have thought about that when i souped it up then started working from home.. i don't get to drive it much anymore.. Anyone wanna buy a camaro??? just kidding...)
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Old 10-01-2009, 05:59 PM   #4
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The coil-condenser combination create an oscillator, so that when the points open, the energy stored in the coil goes into the condenser, then is returned, repeat; multiple sparks actually occur at the plug, transferring the most energy. Since some energy is lost in each spark, the oscillation is damped out. Arcing across the points is reduced by resistance in the lines, not directly by the condenser, although it limits the voltage because of the energy capture. A weak condenser will cause a weak spark, because the voltages will rise higher, but little energy will cycle through the spark plug. If you look at the plug with a weak or open condenser, you'll see a thin, purplish arc, as compared to a strong, blue-white spark. If you double the condenser size, the spark will go reddish, because the voltage will be too low; this also occurs if the condenser is leaking.
BTW, condenser is an old term for capacitor.
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Old 10-01-2009, 06:05 PM   #5
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Quote:
Originally Posted by WintrSol View Post
BTW, condenser is an old term for capacitor.
oooooooohhhhhhhh ... yeah that makes more sense ...

as far as the rest of the info, very useful. thank you
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Old 10-01-2009, 06:53 PM   #6
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If you really want to know, a Wiki covers it well enough:
search for 'kettering ignition wiki' and you'll get it.
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Old 10-01-2009, 07:38 PM   #7
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Quote:
Originally Posted by WintrSol View Post
If you really want to know, a Wiki covers it well enough:
search for 'kettering ignition wiki' and you'll get it.
na, i got it.... i'm familiar with capacitors... just didn't realize a condenser was one. everything fell into place once i learned that.
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Old 10-03-2009, 04:55 PM   #8
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but then Capacitors are only in old bikes? or they are in all bikes? and it doesn't always in action, right? does the capacitor charge up all the time or only when we turn to the first click on the key ?
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Old 10-03-2009, 05:37 PM   #9
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Im going to venture to guess that capacitors / condensers are only in points type motorcycles in the form they are being described here, but given i'm the one that started this thread, i'm obviously not sure.

If i were to guess, electronic ignition bikes probably have them too but they are going to be different from what i've been talking about here.

basically, if the bike has an alternator instead of a magneto (like mine (see note below)), the power goes from the battery to the alternator, the alternator uses that and generates electricity which goes to the capacitors... when the points are closed, the capacitor shoots the electricity across the points up to the coils and into the spark plug and the spark plug fires the motor.

when the points are open, it stores temporarily into the capacitor waiting for them to be closed again...

so technically, if i guess correctly, the capacitors do not hold a charge when the motor is off, since it expends it's energy when the points close, and, even if you turn the key off on the bike, the motor still moves a few revolutions before it turns off, therefore -should- in my theory eliminate any electricity that was previously stored in them...

on the other hand, you're not supposed to take computer monitors or tv's apart because the capacitors in them DO hold charge and can shock the hell out of you... car stereo capacitors for amplifiers and things like that need to be pre-charged when you install them, and i believe they hold that charge for a long time, but are constantly replenished by the current going to it when the car is on. they use these to help get energy to high wattage amps so you don't fry your alternator with too high of a load.

someone please correct me if i'm wrong about all of this... but, i think i'm at least 95% right.

(note: not all bikes have alternators, lots of them have magnetos... the difference is, with an alternator, you HAVE to have a battery in order for the motorcycle to start... a magneto system will allow the motorcycle to run with or without a battery.... on a side note, if anyone knows how to do an alternator to magneto conversion please let me know! i hate having to rely on my battery being charged to start my ****ed bike. it's a scary thought.)

Last edited by mitchberry; 10-03-2009 at 05:41 PM..
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Old 10-03-2009, 08:49 PM   #10
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External capacitors only appear in ignitions that use points; many bikes now use transistor ignitions, but the capacitor is still there, just inside, and the transistor takes the place of the points. The capacitors aren't charged - the coil is charged with a magnetic field when the points close or transistor switches on. When the points open/transistor switches off, the charge in the coil is transferred to the capacitor, and then is transferred back, several times, creating the spark through the other winding of the coil.
Even CDI ignitions, which are rarely used, if at all, have a capacitor, but in that case, the capacitor is charged to about 300 volts, similar to the flash unit in your camera. That charge is switched into the coil to generate the spark through the same oscillation as the points system. They cost a lot more to make than transistor ignitions, which is why you rarely see them, even though many mistakenly call the transistor ignition box a CDI.

The alternator used in most bikes uses permanent magnets as the field, unlike the electromagnets used in autos. Because of that difference, bike alternators need no battery power to generate current to charge the battery and run the lights, etc.

A magneto is a spark generator that uses a magnet which moves past the coil to create the spark; some have points to control when the spark occurs. You seldom find them on engines larger than your lawn mower nowadays, because they're just not reliable enough for a high-performance engine that also has to meet emissions.
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