76 GT500 Not Charging

[MonkeyWrenchCycles]

It starts and runs fine but the charging system is not working. Shows no charge with a multimeter. How do you test the charge coil? Im sure there is a resistance test for it correct? Also how do you test the voltage regulator? Thanks in advance

[jabcb]

Wiring diagram for T500:
http://smokeriders.com/diagrams/Suzuki/ ... Wiring.gif
Wiring diagram update for GT500:
http://smokeriders.com/diagrams/Suzuki/ ... Wiring.gif
http://www.ozebook.com/compendium/t500_ ... 00wire.jpg

To check the stator (charging coil):
1) check resistance between G/W & Y/G wires. Should be about 1 ohm.
2) check resistance between R/G & Y/G wires. Should be about 1 ohm.
3) Check resistance between each of the three wires and ground. You should not get a reading.

To check the rectifier:
1) check the resistance between each yellow wire and ground
2) reverse the meter leads and recheck the resistance between each yellow wire and ground
You should get high readings for one test and low readings with the meter leads in the other direction
3 & 4) repeat the tests for each yellow wire & the red wire
Again, you should get high readings for one test and low readings with the meter leads in the other direction
Note: instead of two yellow wires, you might have R/G & Y/G wires.

The wiring diagrams show the voltage regulator as having only two wires:
1) R/G wire connecting to stator AC output
2) ground wire
Is this actually the case?

What is the resistance between the two voltage regulator wires?
Check the wires, switch the meter leads & check it again.

Does the problem occur with the lights on, off and both on & off?

replacement parts:
Stator coils are still available from Suzuki. Didn't see any used stators/magnetos available on eBay.

If you replace the rectifier or voltage regulator, its worth switch to a modern parts.

[oldjapanesebikes]

In addition to jabcb's comments, this site has some useful info.

[cyclebuster]

Read this you will learn all you need.
BTW, if you hook a household light bulb in between any and all combinations of those 3 wires it should light up at around 2500 rpm.

http://www.thegsresources.com/garage/gs_statorfacts.htm" onclick="window.open(this.href);return false;

[jabcb]

MonkeyWrenchCycles, your GT500 has a different type of alternator than the GS bikes described in the link. The testing instructions are only partially applicable.


Cyclebuster, that looks like a nice write-up on the GS alternators, but the alternators are different.
Thanks for the link. We should add the same type of info to this forum.

The GS bikes have a three-phase alternator with a permanent magnet rotor. (At least that's what the write-up discusses.)

The GT380/GT550/GT750 have three phase alternators with electromagnet rotors (i.e. field coils).

The T250/T350/T500/GT500 have two phase alternators with a permanent magnet rotor. They also use a lighting coil -- part of the alternator is switched off when the lights are off.

[rbond]

The charging is very basic on the GT500. Two coils on the stator, one for daylight, the second one comes on-line when you turn on the headlight. Then it goes to a rectifier to change the AC to DC to the battery. The regulator simply shunts any excess current to ground and heat to control charging of the battery. Very first thing though is to check ALL of your electrical connections for corrosion, tightness, especially to the ignition switch. Then use an OHM meter to check the resistance from both charging coils are 1ohm each. Connect one lead from the meter to the yellow/green tracer, the other to red/ green tracer, should show 1ohm. Again one lead on yellow / green tracer, the other on green /white tracer, should read 1ohm. If no reading, the coil maybe have an 'open' , if too low, a partial 'open' both of which means replacement. Before you order anything, pull the rotor off an check the wires to the coils, one may have vibrated off and needs to be re soldered and sealed again with epoxy. The rectifier is usually the next culprit, again use the meter to check for a reading when connected one way and no reading when the meter leads are reversed on the same two connections. The diodes in the rectifier simply stop current from going 'backwards' of the AC current in order to 'make' DC to charge the battery. If the regulator is bad, I think it would not stop the charging, but I maybe wrong on that. A rectifier suitable for this can be had from Radio Shack, a regulator from Electrex in England, and the stator coils from Suzuki. I hate electrical stuff, it seems more time consuming than anything else.

[MonkeyWrenchCycles]

Anyone have any pictures of how the wires go on the charge coils? I know how the wires go on the two smaller coils for ignition but am unsure how they go into the two bigger charge coils. All the diagrams ive looked at dont show clearly how they go. They list exciter coil and two charge coils but dont show how the wires actually connect.

[MonkeyWrenchCycles]

Got the charge coils fixed but found out the regulator is bad. I saw mentioned in an earlier post that Electrex in England has them. Is that where i should order from? Anywhere in the states that has this? I got on electrex website and found the part with shipping $59. I tried to checkout but it wouldnt do anything but tell me "verified" For the life of me i cant figure out how to process my order...

[jabcb]

Oregon Motorcycle Parts has a nice voltage regulator for the GT triples.
See part VR3-SGT on: http://www.oregonmotorcycleparts.com/vregulators.html
Its $52 and is a direct replacement. Only will need to swap out the connector plug with the one from your old regulator.

[MonkeyWrenchCycles]

Oregon Motorcycle Parts has a nice voltage regulator for the GT triples.
See part VR3-SGT on: http://www.oregonmotorcycleparts.com/vregulators.html
Its $52 and is a direct replacement. Only will need to swap out the connector plug with the one from your old regulator.

Thanks but mine isnt a triple. Its a GT500 so its only a two wire.

[jabcb]

Oops.

I used a Tympanium regulator/rectifier on my T500. It replaces both the voltage regulator & rectifier.

Its available for around $50 on eBay: http://shop.ebay.com/i.html?_from=R40&_ ... Categories
Get one with 4 wires. The ones with 2 wires are actually AC voltage regulators.

It mounts easily to the frame where the old rectifier was.
One drawback is that you have to rig up your own wiring to connect it up. Definitely not nearly as easy as the parts for the GT triples.

[MonkeyWrenchCycles]

Oops.

I used a Tympanium regulator/rectifier on my T500. It replaces both the voltage regulator & rectifier.

Its available for around $50 on eBay: http://shop.ebay.com/i.html?_from=R40&_ ... Categories
Get one with 4 wires. The ones with 2 wires are actually AC voltage regulators.

It mounts easily to the frame where the old rectifier was.
One drawback is that you have to rig up your own wiring to connect it up. Definitely not nearly as easy as the parts for the GT triples.

So how would you wire that up?

[jabcb]

This is how I mounted the Tympanium regulator/rectifier.
Its larger than the T500 regulator. I don't know where the GT500 PEI box is located -- you might need to mount the regulator/rectifier in a different way. Also, one of the bolts attaching the battery box will need to be replaced with a shorter bolt.

T500_tympanium.jpg

I modified this T500 wiring diagram to show the changes: http://www.ozebook.com/compendium/t500_ ... 00wire.jpg
Here is the modified diagram:

t500wire_tympanium.jpg

The Tympanium ground wire is brown as I've shown.
I used a green wire because its commonly available.
I soldered the 3 "Y" wire connections ( yellow to green & green, red to red & red, black to black & black).

The 4mm bullet connectors are available at http://www.vintageconnections.com/" onclick="window.open(this.href);return false;

[geck0]

These are the locations of the Rec/Reg of the GT500A

The Rectifiers are different on the T500 to the GT500. Would the Rec/Reg combo work on his GT

[jabcb]

Would work just fine.

I thought the PEI box might be located under the seat & in front of the voltage regulator. That would have precluded mounting the Tympanium the way I did. Given your pic, that's obviously not the case.

Since the GT500 rectifier uses a latching connector, it will be less work to install a regulator/rectifier.

If you install the Tympanium the way I did, make sure you get a shorter bolt for the battery box. Since one of the bolts no longer secures the regulator, it long enough to penetrate the top of the battery.