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1975 Yamaha DT 125


Rattlesnake
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I bought a 75 DT 125 a year ago and been working on it here and there. I am not very familiar with the electrical system on this bike but do have a service manual and am muddling my way through it best I can. It does not have a good battery in it right now so I have to have it hooked up to the charger to run. Should this bike start without a battery when it is kicked or does it have to have a power source to initially start, even when kicked? I am more familiar with the 2 strokes that have a mag. Once I get it started it will stay running without a power source as long as the RPMs are kept up a little.

Ray,

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Hi rattler" yes it will start without battery. and run perfectly, :yeah: turnsignals etc , will not flash , you will get headlight tho. and neutral light, it is a 6VOLT SYSTEM, mind when charger is fitted,, :welcome:

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Blackhat, I do obviously plan on getting a battery for it in a day or two, but I am monkeying around with it a little in the meantime and it does not seem to be producing a spark without the charger on the battery (battery is shot). It does start and run when the charger is connected. Once it is started it will run without the charger as long as the RPMs are kept up, it wants to die if it is allowed to idle for more than a couple seconds and then will not start again (by kickstarter) until the charger is reattached. I did notice the armature has a couple broken wires on the area where the bars connect to the commutator. What problems can this cause? It also has a broken brush. I guess I am concerned about its ability to charge if it can't produce a spark without a battery. Sorry for the rambling, but this system for starting, charging is different than anything I have had before.

Ray,

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Take the battery out it's taking all the charge from the mag.Then it will probably start.

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Hi

As others have posted Dt's can run without a battery, reading your post is your bike a DT125 with an electric start as well as a kick start? Maybe 'AT1-C, AT2E,AT3E' if so my manual has these listed as having 12 volt 7 amp/hr batteries,

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Hi

As others have posted Dt's can run without a battery, reading your post is your bike a DT125 with an electric start as well as a kick start? Maybe 'AT1-C, AT2E,AT3E' if so my manual has these listed as having 12 volt 7 amp/hr batteries,

A good point.

Rattlesnake, what is the first part of the frame number? The old mag type bikes normally need a decent battery to start them (even with the kickstart) and should be connected to some sort of battery when running.

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A good point.

Rattlesnake, what is the first part of the frame number? The old mag type bikes normally need a decent battery to start them (even with the kickstart) and should be connected to some sort of battery when running.

Thats what I was thinking, the bike may need higher revs to make the starter /mag work harder to make up for a weak 12 volt battery

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It needs the battery to run at low rpm. If its running without the charger it may be feeding some power.

The broken armature wires are a worry and should be fixed as yam obviously wanted them connected.

Try and sourse a good battery, then see what the voltages are. You will need a manual to check it properly.

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Hey guys

All good info that will help me work through this. The numbers for my bike (on the frame and engine are the same) 444-123144. I was able to find a shop that does electric motor repair. They told me the armature was no good because of the missing wires, so I think I will try and find a suitable replacement. I have some difficulty finding an armature, it seems there are at least two different sizes and of course I must have an odd one. It measures 3 1/4" shy sitting flat as in posted picture, and 3 5/8" diameter, so any help there would be appreciated. What are your guys thoughts on the armature being no good? Thanks fellas.

DSC01661_zps465c8caa.jpg

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Its a DT125 B -1975 . :jossun: you should get a rotor for them on Ebay,,, these are 6 volt system ..

2011%5C04%5C23%5Cbikepics-2194349-full.j

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  • 2 years later...

hi im new on here ,,,,,,hi to you all ,does all thats been said here also apply to a dt50 1991? i want to strip off all electric s i  don,t need exept for running for fun up the dirt track with my grandkids ie engine electrics only.Im sure someone could advise me what to keep and what i can strip off.looking forward to contacting like minded people. cheers

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