Author Topic: Yamaha ycs1 180 twin, dynamo  (Read 117 times)

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Offline Curtie94

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Yamaha ycs1 180 twin, dynamo
« on: August 11, 2017, 01:24:32 AM »
So I picked up a 1968 yamaha ycs1 about a month ago. Cleaned it up. New pistons, rings, seals etc.

I took it out for a ride and after about an hour or so the charging light came on. Went home and found that the voltage barley changes on the battery when running.

Battery voltage 12.3v not running. 12.7 running 2000 rpm. Does not go any higher.

So I looked at the manual and tried to follow the instruction. By disconnecting both wires that go to the regulator, grounding the green terminal  and checking voltage output from the white terminal but my meter reads .7v

So either I'm doing something wrong or it's not charging.

Are there any common issues?

Also is any part of the dynamo supposed to be magnetized?

Electric start works perfect. There is 1 brush that is worn more then the others but not horrible.

The charging light goes out now off idle. But my battery voltage peaks at 12.7 to 12.8v when revving and drops to just below 12v at idle. Shouldn't it be more?

Any help would be appreciated

Thank you
« Last Edit: August 11, 2017, 01:26:27 AM by Curtie94 »
1976 RD400
1968 Yamaha YCS1
1965 Honda S65, 1972 CT90
2015 Yamaha FZ09
2015 Honda CRF250L

Offline Motty

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Yamaha ycs1 180 twin, dynamo
« Reply #1 on: August 11, 2017, 06:08:53 AM »
If you have a look in the "Skill Centre" you will find a Charging Check Flow Chart. I have found this helpful to identity where the fault lies, although I would expect your problem is a broken or corroded connection

Happy hunting, I hope you find the fault easily :)

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Offline Curtie94

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Re: Yamaha ycs1 180 twin, dynamo
« Reply #2 on: August 14, 2017, 01:53:46 AM »
So I tested the generator and am getting 15-20v. Just off idle.

So I put it back together and it was charging. But I found that after a minute or 2 it would stop charging again. But here is the kicker. If I press the start button while it's running it starts charging again until I let it idle then it stops charging again.

The only thing I found that I do have to fix is 1 of the springs that holds the brush In is missing. 1 of the range is broken so I can't even install another spring.

Any ideas on installing another brush spring. Maybe solder a compression spring to the case and let it hold pressure on the brush?

But even with the brush contacting it doesnt charge until I press the start button. Could it be inside the regulator?
1976 RD400
1968 Yamaha YCS1
1965 Honda S65, 1972 CT90
2015 Yamaha FZ09
2015 Honda CRF250L

Offline Motty

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Yamaha ycs1 180 twin, dynamo
« Reply #3 on: August 14, 2017, 07:06:01 AM »
Where are you getting 15~20v? Hopefully not at the battery.
Can you post a photograph of the problem with the spring?
I assume if one is damaged you should be able to replace either the spring or the brush AND the spring if it is a combined unit.
Have you looked at images of a RD200 generator, as yours should be similar if not the same, a check of the part numbers will confirm

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“...inside every old person is a young person wondering what the f*@k happened.”
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Offline Curtie94

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Re: Yamaha ycs1 180 twin, dynamo
« Reply #4 on: August 14, 2017, 05:53:09 PM »
I was getting the 15-20v at the generator after full fielding it. I followed the manual to correctly check generator output.

As for the brush spring. I am currently at work so I can't take a picture but I have no way to install another spring because the tang is broken off the generator case.

There is 2 metal tangs/pins that come off the case to secure the spring. And I can not attach another spring because there is only 1 left.
1976 RD400
1968 Yamaha YCS1
1965 Honda S65, 1972 CT90
2015 Yamaha FZ09
2015 Honda CRF250L

Offline Motty

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Yamaha ycs1 180 twin, dynamo
« Reply #5 on: August 14, 2017, 11:48:48 PM »
If you can get a photo of the issue and start a new topic in "RD200 and under", you stand more chance of finding someone who might have come across this problem before
I am reasonably sure that your rotor/generator will be similar/same as a RD200

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“...inside every old person is a young person wondering what the f*@k happened.”
Terry Pratchett