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  • msavitt
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stupid question was created by msavitt

1978 DT400E

Magneto has three coils:
- Pulsar coil
- lighting coil
- source coil

Is the pulsar coil what energizes the CDI?
Lighting coil provides AC to headlamp and gauge backlights?
Is the source coil what charges battery?  Is the term "source" used synonomously with "charging coil"?

thanks for your help
14 Jan 2022 08:55 #1

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Replied by Grussell on topic stupid question

If I remember correctly the Pulsar coil sends the timing signal to the CDI to discharge to the ignition coil. Lighting coil powers lights and charges battery, source coil charges the CDI box. The Lighting coil uses bigger gauge wire with less windings because it only provides 6 volts for the lights and battery. The source coil uses smaller gauge wire with many windings increasing resistance and maximizing voltage without overheating.
1978 DT400
1975 DT250
1976 YZ125X
1976 YZ125C - future project
1976 YZ125X - future project
2018 YZ250FX - my race bike

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14 Jan 2022 11:02 #2

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Replied by msavitt on topic stupid question

thanks Mr. Grussel!
14 Jan 2022 12:16 #3

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Replied by RT325 on topic stupid question

 Not a stupid question & electrics & electrical terms can be confusing & ambiguous at times with the likes of cdi charge coil & lighting/charging etc .
Did a bit of a trick on my RT2motor yesterday with a damaged DT360A stator. Removed lighting coil & had a piggyback smaller coil on the cdi charge coil but had lighting wiring so not a cdi high speed coil, just lighting involved. So 'that' out of the way I inspected the charge coil--super fine wire that was damaged & stray bits of wire hanging off. Had continuity of about 300ohms so tested peak voltage at about 90 at kick speed & only just over 100 spinning it with a drill on the crank nut. So found a cdi box coil combined off an RG50 Suzy. One wire from source coil to that coil/box & sparked & guessing timing by feel of tdc then back a bit, i chalk marked the flywheel & a case screw hole as a reference mark then strobed it spinning with drill. Was pretty close to the mark. So kick kick & backfire & kick back & thought bugger--i'll break something. So fully retarded the stator plate & same deal. So further retarded the flywheel minus the key & still similar & no chance of starting. I always think the source need about 160 peak volts at kick speed to run. Plug lead i'd used was a high resistance 'non wire' oldy of my old car. So used a copper wire & non resistor cap & set timing back to how i started & damn it she started up & sounded good. Been down the road once so that could change haha. I have an 'EI' Carb [like a Blue Magnum i think] on it i've never used so learning curve. No jets & all needle controlled. Bought second hand many years ago. So anyway--she runs & a simple system with no trigger/pulse coil. Coil/box has one wire in plus an earth to the frame. Sorry OP, getting way off course from your question. I might copy this story & start another post later to see what tricks people have come up with.
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Last edit: 14 Jan 2022 14:42 by RT325.
14 Jan 2022 14:41 #4

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Replied by adguy2112 on topic stupid question

My wife in looking a my retrofit ideas always says I should have been an engineer. After reading your posts RT I think what an imposter I'd be compared to someone like you. I'm always blown away by your tricks but I'd have say I'd be scared to own a bike that you built...not because it wouldn't run like a champ but because I wouldn't know what to do with it if anything ever went wrong. Duly impressed, sir!
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14 Jan 2022 14:59 #5

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Replied by msavitt on topic stupid question

RT is indeed creative and resourceful!

My source coil had the lead broken off....I re-soldered and epoxied over it all when I rebuilt it and it is a one kick wonder.  Reason I asked was my turn signals are not flashing quite right because battery is low despite putting out over 7V when reved up....but headlight is bright as heck, so I am thinking its my battery shot or one of the two taps off the lighting coil charges the batter and is out of spec.   I am going to try another battery before messing with lighting coil as these are pretty rare and expensive and in the end everything works terrific, albeit with rapid but limp twinkers
14 Jan 2022 16:17 #6

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Replied by RT325 on topic stupid question

Yes, pity any brave soul that buys any of my stuff if it goes wrong haha. But if i did sell anything they'll be fully aware of its dodgy things involved "& 'must' have a plan".
Anyway, with the [limp twinkers], what wattage bulbs are they, & are they 6 volt not 12. If you bypass the flasher relay & just join the wires are they any brighter. Does it charge more than 7 volts to the battery with the headlight off & give brighter flashers. Bulbs need to match what's written on the relay or slightly more for a faster flash, but only talking say 8watt to 10 watt difference like older scooter had. Yours might have 17watt bulbs so they draw a bit for sure. Bit out of my league really but does it have a regulator & is it 'over-regulating', although i guess its doing its job if the headlight is bright but not blowing.
14 Jan 2022 19:54 #7

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Replied by MarkT on topic stupid question

Flasher unit might be suspect.
1963 YG1-T, 1965 MG1-T, Allstate 250, 1970 CT1b, 1971 R5, 1973 AT3MX, 1974 TS400L, 1975 RD350, 1976 DT175C, 1976 Husqvarna 250CR, 1981 DT175G, 1988 DT50, 1990 "Super" DT50, 1991 RT180, 2017 XT250
14 Jan 2022 21:02 #8

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Replied by msavitt on topic stupid question

thanks
6V bulbs 8w X 2 on L and R
flasher says 35 candle power, wattage who knows
so I ordered up a 17W flasher for a few bucks
15 Jan 2022 13:44 #9

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Replied by RT325 on topic stupid question

That'll make the battery work hard "17 watt" but yes i think 32cp is 17watt by memory as think it had both numbers written on those big flasher units although might be confused with 12 volt ones that bigger road bikes used. For the sake of the battery you might be better to get a relay to match your 8watt bulbs. Best of luck.
Just thinking back 17watters are a bigger bulb so hope there's enough depth in the flasher to accept them.
Last edit: 15 Jan 2022 14:05 by RT325.
15 Jan 2022 14:04 #10

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