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Old 08-13-2014, 10:35 PM   #1
dhallilama
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Default magneto condenser / ease of starting discussion

chevelle brought up something interesting regarding the magneto primer/sticky that has me questioning what i've always known (thought?) regarding mags and low RPM (starting) operation...

here's what i've always thought: the higher mfd (within reason) the easier the mag fires at low RPM. really thinking about this, it doesn't necessarily make sense. lower capacity (mfd) might have a higher voltage at low RPM, yes? if so, that kinda turns what i've been going off of upside down.

care to discuss?

the common condensers i know of are:

Morris P6 ( ~.20mfd)

FM AXMR2433 (~.22mfd)
NAPA SME 701308 ( ~.22mfd)

Accell's "high performance" ( ~.26mfd)

FM SXY2433 ( ~.32mfd i think)
NAPA FM 200 (same as above)

FM RX2433 (.48mfd... never ran one)




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Old 08-13-2014, 11:53 PM   #2
LivingCanvas
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Default Re: magneto condenser / ease of starting discussion

Hey I had just came to the same conclusion! I do a lot of reading and searching on this site trying to gather as much info as possible. I also thought higher is better. Then I read the same info in the stickies...

Inquiring minds want to know
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Old 08-13-2014, 11:59 PM   #3
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Default Re: magneto condenser / ease of starting discussion

Not higher voltage, that will be constant The higher capacity cans should deliver more current, but the cycle time would be slightly longer.
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Old 08-14-2014, 12:09 AM   #4
dhallilama
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Default Re: magneto condenser / ease of starting discussion

i swore there was something about it in How to Build a Harley-Davidson Torque Monster by Bill Rook... but i can't find my copy & google books is missing page 61(ish)

so, if the lower mfd condenser = a higher low rpm current, it would (i assume) also = easier starting? with the drawback being high rpm issues...

i may have been dead sure about my previous assumptions (which is where the sticky info came from). always willing to learn...
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Old 08-14-2014, 04:26 AM   #5
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Default Re: magneto condenser / ease of starting discussion

A higher capacitance can store more energy in the capacitor and will deliver a hotter spark / higher voltage compared to a lower capacitance at the same RPM.

Energy in a capacitor is E=1/2 x C x V^2 with C the capacitance and V the voltage, which is related to the RPM. In practice when the points open and the voltage in the coil is transferred to the secondary side, the capacitor "slings" the voltage up to an even higher amplitude. The more capacitance, thus the more energy stored, the higher the voltage gets "slung up"

It is most handy for magneto's with kick start only. The downside is, you'll burn your points faster. Nowadays Morris M5 capacitors standard is 18uF and the higher capacitance is 26uF.
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Old 08-14-2014, 08:46 AM   #6
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Default Re: magneto condenser / ease of starting discussion

I had Hank at Morris give me their (I wanna say) "S" condenser a couple of years ago. It's considerably larger than the "P" or "R", but I'm unsure of the capacitance, but I know that it starts a bit easier than with the "P" that was on it originally. It was at his suggestion that I try it out and I was pleasantly surprised.
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Old 08-14-2014, 08:47 AM   #7
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Default Re: magneto condenser / ease of starting discussion

hmm. interesting discussion. I don't really know about points and magnetos but I have read some ignition threads over on the jalopy journal. there is an ignition guy over there who posts up some information, tutorials and such. GMCbubba is his SN. He posted up that if you have the wrong condenser in a regular distributor it will severely effect point life. basically he said that by checking which side of the points are burnt will tell you if you have too much or too little capacitance in your condenser. He never really mentioned it having an effect on power or starting.
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Old 08-14-2014, 10:54 AM   #8
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Default Re: magneto condenser / ease of starting discussion

This is awesome thanks for starting this, I haven't done all that research etc. I just was amazed at the difference it made when I switched my old one which I don't know what it was no marking to a fm200.
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Old 08-14-2014, 11:26 AM   #9
Dave B
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Default Re: magneto condenser / ease of starting discussion

Throw the Accel ones right in the garbage. If it is not a F-M condensor you are annoying yourself for no reason.
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Old 08-14-2014, 12:55 PM   #10
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Default Re: magneto condenser / ease of starting discussion

dhalli,
I'm not sure how it relates to kick-starting vintage bikes, but the mofos at the Moco determined that condensers with a higher micro-farad rating (like .30 m.f.) gave better performance (especially points life) at lower rpm's and speeds, and condensers with a lower m.f. rating (like .18 m.f.) functioned better at higher sustained speeds. This info relates primarily to the police bikes the factory supplied. Think "meter maid" machines for low speed, and State Highway Patrol for high speed. The "middle-of-the-road" condenser for regular use was .23 m.f.. There is some further information in Palmers book.

Geo.
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Old 08-14-2014, 01:27 PM   #11
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Default Re: magneto condenser / ease of starting discussion

Quote:
Originally Posted by Dave B View Post
Throw the Accel ones right in the garbage. If it is not a F-M condensor you are annoying yourself for no reason.
the only two times in my life a condenser went out on me, leading to changing it on the side of the road, they were Accel. (neither on Harleys)
the only two times coils shit the bed; Accel.

I don't buy anything from them anymore.
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Old 08-14-2014, 10:01 PM   #12
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Default Re: magneto condenser / ease of starting discussion

Here is a bit of info regarding the FM magneto condensers for XLCH's.
Pretty much sums up what I've found researching condensers for mags.

http://xlforum.net/vbportal/forums/s...1&postcount=50
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Old 08-15-2014, 01:26 AM   #13
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Default Re: magneto condenser / ease of starting discussion

well... Dr Dick does seem to know his shit (read a ton of his posts over the years)...

though it contradicts what i've heard over the years (more or less what C1340 stated, above).

all interesting stuff...
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