Roketa 79-250 charging problem By Bashan (Read 3,492 times)

[kenneth36laughlin]

I'm a new member with a Roketa 79-250 with a charging problem. Checking the three yellow wires in series like this:

I get 40v -40v- 36v. I get 12.2v, plus or minus .5v, across the black and red battery wires disconnected from the battery with motor running. It is apparently is enough to keep the motor running, but the bat slowly runs down. I strongly suspect the magneto. Appreciate your opinion. thank you.

[tvnacman]

Were the readings taken at idle ? If so rev to about 4 or 5 thousand rpm and hold for 30 seconds with the stator unplugged .you should close to 60vac yellow to yellow in any combo . Report your results .

John

[Bashan]

Yes exactly John. Also, you don't have to unhook the battery to read it's charge, you can just touch the meter probes to the terminals. The 12.2v DC is too low, it should be 14 or even a little higher.

Here's more tests you can do on the stator, unhook the three yellow wire connector to the stator. Also, unplug the auto-choke since it will gound the stator. Then check for continuity between the three stator yellow wires two at a time:

You should have continuity between the three wires as you can see in the diagram they're interconnected. If you don't have continuity on two of the wires that's a burnt coil and the stator is toast.

Now check each yellow wire for continuity to ground. You should NOT have continuity to a ground. If you do it's a short and the stator is toast.

As I said, your bike may be wired so that one of the yellows provides power to the auto choke. In that case that will provide a ground for all three wires so you must unplug the choke to run tests to ground. Here is the three wire connector on my CF Moto Fashion and you can see the yellow wire running to the auto-choke. This must be unplugged:

[kenneth36laughlin]

Finally got the wife to hold throttle at 4K. Readings are 50v ac between each of the three yellows, plus or minus 1or 2 volts. Continuity of each lead to ground is neg. This would indicate to me that maybe I should pull all the shrouding so I can get to all electrical plugs and check the voltage at the battery while checking all the plugs, maybe a bad connection, which I did find earlier on the red wire from the "monostat", which I assume is the regulator and/or rectifier. the diode at the red line at the battery pos terminal checks OK.

[tvnacman]

What is the voltage at the diode ,list both side voltage measurements . With tne engine at 4000rpm and all plugs pluged in .

John

[Bashan]

Great call John, that may very well be the problem. Kenneth, I wanted to expand on something, you can test a yellow wire in series with the multi attached in the middle of the wire like this:

When I do that with my Fashion 250 I get 73v AC:

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Now you can test between two yellows like this:



And when I test that way I get 86v AC:

Both ways of testing evaluate the amount of current moving back and forth (AC current) through the multi. So with some RPMs you should get in the 70s or 80s in AC voltage either way you test it. If you don't it's probably a bad stator and your 50v indicates a potential problem. If you do get those voltages then the stator is doing it's job and the regulator is probably the culprit.

John has an excellant point though that it might be the diode. I don't have a diode on my bike so I tend to gloss over that aspect of the charging system which is my bad. Just to make sure we're on the same page the diode will look like a small regulator (yes...monostat) but will only have a two wire connector:

As John said pop the connector and use your multi's diode function or simply test ohms going both ways. You should get voltage only in one direction, if not it's the diode.[/b]

[kenneth36laughlin]

Hey, I finally found a place to answer. Fri morning I removed all forward shrouding to get to voltage reg and rectifier. checked all plugs, then started scooter in the dark to check for a possible arcing. This was negative so started the testing of each of the magneto wires. I tested them by removing bayonet part from plug, so remaining two leads would still be connected. These results were 21 to 24v idle, and 40-42v at 4K. Measuring between two of the yellow leads while running gave 30-40v ac. I had checked the diode with an ohm-meter before, shows open one way. short the other. Voltage running at the diode- Idle 12v line side, 13.7 battery side, and at 5K 11v line side and 14.7v bat side. Needless to say, the voltage across bat terminals now was 14.2v. Good news and bad news. Battery is charging fine now, but I haven't a clue why. With the voltage meter still attached and motor running, I tried everything I could to find bad connection. It is all back together now and is going down to a lot with a FOR SALE sign. Thank you for the suggestions, and help.

[Bashan]

Yeah, those values from the multi are essentially normal. I don't start getting 70 to 80v AC until the engine is wound out to 5K or higher. I still think you've got a hinky stator and I'd replace it and see how it does. But we understand your frustrations and desire to get rid of it. Let us know if you sell it and maybe you'll feel like riding it after the dust settles.

[tvnacman]

one of the plugs or connections was loose or weak connection causing the problem . It happens to the best of us . I would check all the ground points be sure they are clean and tight .

John

[Bashan]

I got involved with this thread because Kenneth PM'd me and asked for some help since he had no experience using a forum, or computer for that matter. Kenneth has decided to chuck his scooter but I've received quite a few PMs about the stator testing. So I thought I'd try to clear things up for everybody all at once.

My bike may be wired different than others, all I can do is tell you how mine is configured. A few guys were adamant that I did not need to unplug the auto-choke to test the continuity on the yellow wires. Well on my bike the yellow wire that splits off to the auto-choke is on the stator side:

So if I unplug the stator harness and leave the auto-choke plugged in I get a continuity to ground through this path:

That would be a bad thing if it wasn't due to the choke ground because it means a short from the stator to the case:

You would in fact get a tone on any of the stator wires with the choke plugged in since they connect in the stator:

So unplug the choke and the connection to ground is gone:

So you should not get continuity from a yellow to ground but you SHOULD get continuity from yellow to yellow:

If you don't:

Here's my Fashion's wiring, you can see the AC to the auto-choke split off from the stator side. If it was on the regulator side none of this would be an issue. I must admit I spent almost an hour trying to figure out why I kept getting continuity to ground yet the stator charges just fine:

The green ground wire from the auto choke along with the temp sensor wire return in the sheath to the red connector.

[tvnacman]

I think we got this one solved , I think the cooling fan was jumped and running all the time.
John