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Makotosun

1975 DT125 Generater/armature help

  • willhirsch
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1975 DT125 Generater/armature help was created by willhirsch

Hey guys,

I have a 1975 DT125 (444-123144). When I got the bike it was missing the armature and the cover for it, I do have the generator but none of the fastening hardware. My question is should I get a spark with a fully charged battery when I try to kick start it? When i try the electric start i just get a single click?

Thanks in advance!
03 Aug 2015 09:45 #1

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Replied by Bigdog302 on topic 1975 DT125 Generater/armature help

I would ask Capt Dave about this. he is the electric start Yamaha 125 guru pretty much.
2 1968 DT1s,1970 RT1M,1970 DT1C,1971 RT1B,1971 Honda Z50K2,1974 DT100A 1974DT250A,1974 Honda MT250,2 1975 DT400Bs,1975 Honda CR250M1,1978 DT175E,1979 Honda CR250R.
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03 Aug 2015 15:10 #2

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Replied by Makotosun on topic 1975 DT125 Generater/armature help

The electric start bikes need all the parts there PLUS a fully charged 12 volt battery in order to make any spark at all. The click you are hearing is the solenoid. It is looking for the armature and everything else to work.

I have not looked for the parts, but they are not likely to be still available and will not be inexpensive. The stock system is a bit odd anyway, as it is a starter-generator which acts as a starter when the motor is off, and as a generator when it is running. Just a set of brushes from Yamaha (still available) will run almost $160. Aftermarket ebay sellers can get you a set for about $40.

I with a PowerDynamo 12 volt CDI system recently on my 1970 AT1 (exact same ignition) which eliminates the starter, but gives amazingly great results. You can read more about it here:

yamaha-enduros.com/index.php/forums/rest...t175-sleeper-project

Start about post 22.

Here is the Film at 11:00

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03 Aug 2015 16:59 #3

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Replied by RT325 on topic 1975 DT125 Generater/armature help

Ignore me if this doesn't apply but 1975 DT125EA down this side of the world had a smaller armature & stator. Same 12volt electric start dc system but was a very perky motor & next generation shape motor from the AT1/2/3. Only saying this incase searching for am armature & end up with the bigger diameter one [seeing he still has the original stator. Our electric models were AT1FE [piston port motor] sold lots to farmers & were good 'lazy motor' due to the armature weight & of course when it's charging she's a bit of an 'electric brake'--could pull the charging arm of the regulator up & just about stop the motor [wouldn't do that-would i]. Then nothing electric till the DT125EA probably "74-"75. Had one myself in later years & was good too. Have a magneto AT1 myself now which was dads farm bike & got it as a trade in at work back in the "70's.
03 Aug 2015 17:44 #4

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Replied by Makotosun on topic 1975 DT125 Generater/armature help


That is some good information I was not aware of. I am sure others may know this already.

Powerdynamo makes two different sized kits - I is entirely possible the smaller diameter one would fit. They are a German company so are probably already aware of there being differences in the non-US models? If you were to go with one, make sure to e-mail them first.
IF it isn't one thing, it's another.
03 Aug 2015 18:20 #5

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Replied by willhirsch on topic 1975 DT125 Generater/armature help

Thanks for the replies!

Do you think if I found an armature, and got it put back together I would have a spark? Also I am missing the governor assembly...

This is what I am working with:

04 Aug 2015 09:31 #6

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Replied by DEET on topic 1975 DT125 Generater/armature help

Without the "governor" it won't run.
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Where the Yamaha Enduro is still a current model...
04 Aug 2015 12:39 #7

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Replied by RT325 on topic 1975 DT125 Generater/armature help

Now i'm gettin worried about the info i gave--which i thought was correct for down here --BUT--looking at the pic supplied above & expanding it & turning around, it's the older AT1/2/3 type case, not the next generation, that's if the pic is of yours & not just a random pic? to top that off the generator number changed from 1970 to 1971 [261 to 444] so possibly the smaller armature was used from then on. The motor shape [type] only changed for 'kick start only' models from probably 1974. so i dunno--i'll crawl back in the box!!. Just do your homework or measure in where the armature runs & allow a bit of clearance. Chances are there's more of the right ones around for parts than the very first AT1 electric start. As stated by DEET it needs the governor with points cam incorporated, has a long bolt too that holds the lot from escaping [& locating key in the crank].
04 Aug 2015 16:58 #8

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Replied by RT325 on topic 1975 DT125 Generater/armature help

just thought too, when sliding the stator assembly over the armature--pull the 4 brushes back till the springs pop down beside them which holds them out of the way, otherwise you'll break them as will catch on the end instead of going over the armature [commutator bit].
04 Aug 2015 17:03 #9

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Replied by MarkT on topic 1975 DT125 Generater/armature help


Thank you RT325. I am very interested in your observations of the 125 electric start models having significantly different parts.

I did as much extensive research as I could on the electric start models sold in the USA and Europe from 1969 to 1980 or so. There appears to be a change in the design somewhere in the mid-1970's. But it also appears that as long as you exchange the complete unit and don't try to "mix and match" parts (early armature with later stator or vice versa), the systems are interchangeable.

What I found was that Yamaha kept the AT1 (1969-73) crankcases (130mm stator mounting diameter) and crankshaft on the electric start models to at least 1980. The kick start only models received a newer "small" crankcase in 1974 (120mm stator mounting diameter).

The new smaller case design also moved the clutch actuator mechanism from inside the right side cover (as found on the AT1 design) to the top of the right side crankcase half.

Top of engine clutch actuator design -Kick start only 125's and 175's after 1973:





Side cover clutch actuator design - Kick start 125's and 175's to 1973, ALL electric start 125's:





RT325- do you have documentation that Yamaha had a electric start 125 Enduro model that had the later style top of engine clutch actuator? Or a smaller (120mm?) mounting?

Every electric start 125 I could find had the AT1-style crankcases including the the side cover clutch actuator. I would be very interested to know if there was a different version made somewhere in the world!

Thank you.
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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04 Aug 2015 20:59 #10

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