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1976 DT400 charging?

31 Mar 2020 19:04 31 Mar 2020 19:30 by JimmyC.
JimmyC
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1976 DT400 charging? #1
My DT400 with the battery not connected is only getting 4.6 volts to the + wire going to the battery. The rectifier has checked good (.517) 1 way, open the other way. Connections look great. Headlight gets brighter when I rev the engine. Not sure what to look for. Any help would be appreciated. Thanks Jimmy

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01 Apr 2020 00:14
RT325
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1976 DT400 charging? #2
Not sure myself unless its got a single wire AC regulator & its holding it back due to being faulty, Thing 'is' with your bulbs, if someone's snuck a 12 volt in somewhere it'll hold it back, or if [like us] you have a replaceable headlight bulb & its got a higher wattage fitted, Lower wattage bulbs means brighter lights [weird i know] & consequently more left over for charging the battery. I now see you say minus battery. How does it compare with lights turned off.

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01 Apr 2020 05:57 01 Apr 2020 05:58 by JimmyC.
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1976 DT400 charging? #3

RT325 wrote: Not sure myself unless its got a single wire AC regulator & its holding it back due to being faulty, Thing 'is' with your bulbs, if someone's snuck a 12 volt in somewhere it'll hold it back, or if [like us] you have a replaceable headlight bulb & its got a higher wattage fitted, Lower wattage bulbs means brighter lights [weird i know] & consequently more left over for charging the battery. I now see you say minus battery. How does it compare with lights turned off.


Headlight on or off it's the same. Does the bike have 2 separate charging circuits? I'm thinking yellow wire for headlight and green/ red for battery.

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01 Apr 2020 06:42
RT325
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1976 DT400 charging? #4
I'll let someone else put me right but thought the yellow was the highest output & everything else came off that coil further down the line. i'll have to study a diagram & i'm not good at following them but don't have time at the moment sorry. Maybe [thinking] [for an experiment] you could hook the yellow to the rectifier [where the white hooks in] & see what you get back to the battery just testing across the battery on dc volts or using amps from battery negative [disconnected from frame] to frame earth so the amp meter has the battery earth into one side & other side of meter to earth. Should charge plenty like that especially if no regulator in the mix. If i'm up the creek--happy to be corrected.

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01 Apr 2020 07:38
JimmyC
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1976 DT400 charging? #5
There is a regulator. I think that's for the headlight voltage.

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01 Apr 2020 19:12
JimmyC
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1976 DT400 charging? #6
Simple question. Is there one or two charging circuits on this bike? 1976 DT400.

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01 Apr 2020 19:50
MarkT
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1976 DT400 charging? #7
I'm pretty sure 1976 still had a headlight on-off switch. If so, you should have three systems (not counting the ignition)...

Daytime charging (DC to battery), nighttime charging (DC to battery), and Headlight (AC).

That's if it's stock... if someone swapped out the ignition for a later model with "always on" headlight you'd be missing the daytime charging.

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

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01 Apr 2020 19:59 01 Apr 2020 20:00 by JimmyC.
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1976 DT400 charging? #8
It does have a headlight on/off switch. The bike is 100% stock. If I keep the battery charged with a charger will it be ok for 1hr. rides? Thanks Jimmy

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01 Apr 2020 20:37
MarkT
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1976 DT400 charging? #9
Should be. If battery goes dead if will still run just fine.

Are you checking with engine revved up?

Any difference between lights on and off?

Your problem could be the handlebar switch. The "on-off" for the headlight also switches between the day and night charging. Could have a bad connection in the switch.

I think you said you tested the rectifier... which is just a diode... I just had a bad one that seemed to test fine but wasn't working right. No voltage at all came through on mine. So if you've checked all the connections and everything is good you might try swapping it.

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

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01 Apr 2020 20:42
loner
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1976 DT400 charging? #10
Might be a dirty connector in wiring system, especially in the charging system.

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