1982 Suzuki gs750t wont charge while running.

2018 Views 24 Replies 7 Participants Last post by crazypj, 9 mo ago

Josiah B

Discussion Starter · 11 mo ago

My 82 gs750 won't charge while running. I've been told it's the reg/rec, the battery, or the stator itself. I have a brand new li-Ion battery just installed, so it's not that. Reg/rec is also brand new, but it's possible. Best guess is the stator. Any thoughts?

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TrialsRider

· #3 · 11 mo ago (Edited)

Modern solid state batteries are not suited to old motorcycle charging systems, so your choice of battery is a big problem, Li-ion battery can not tolerate over-voltage or permanent damage results. Your original charging system was designed for a lead acid battery that is very tolerant of over-voltage, basically because it is liquid cooled. Manufacturers designed the charging system around that wet cell battery, not a Li-ion battery type that didn't even exist when your motorcycle was built.

Power generation starts at the alternator coils and magnets so that's the first place to start testing and then work down stream to the rectifier and regulator. The output from the rectifier and regulator needs to be compatible with your fancy expensive battery or else you need to go back to stock everything.

You don't need to guess with electrics because you can test every part if you have the proper equipment. ... except that Li-ion battery, if the battery has been damaged internally there is no test for that, it will just have a shorter life expectancy until it finally melts down, catches fire or just quits working.

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TrialsRider

· #7 · 11 mo ago

I buy the cheapest battery I can source and replace them when they let me down which is not for a couple 3 years, then they give me some money back for the old one, that's hard to beat.
You can regulate the power output you have, unless it's total garbage and you can determine that with an oscilloscope in minutes. You still need to know the charging voltage appropriate to your battery and only the battery manufacturer can tell you that.
Anything short of looking at the output from your existing alternator is just a guess, they output voltage all over the place and that's destructive to solid state devices, you need to clean up the power output.

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TrialsRider

· #9 · 11 mo ago

lol I just checked the price for the 4 tiny little lithium batteries in my TRS headlight,
£ 286.82 plus tax and shipping,
that's 443 Canadian$ FOB England

like that is going to happen. I guess I'm trading in my TRS when the battery gets old.

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TrialsRider

· #11 · 11 mo ago

How come when you click on any of Rick's Rectifiers it says currently unavailable

This is probably closer to what you really need anyway:

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TrialsRider

· #18 · 9 mo ago

Are you starting out with a fully charged battery (charged from a wall outlet)
Lithium battery is happy to take a charge as fast as you feed it.
The whole idea of the LED lighting is to reduce power requirements so possibly your lighting setup is flawed. I guess first test would be disconnect the lighting and try again, if she still dies your battery is not charging and it's the ignition that is sucking back power or the battery is simply not charging.

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TrialsRider

· #19 · 9 mo ago (Edited)

Josiah B said:
...What is mis connected to cause the battery to affect the motor?

Your motorcycle has a battery and coil ignition, meaning the coils powering the spark plugs run off the battery. Insufficient battery power = no ignition & bike stops. No battery and the bike won't start. You should invest in the cheapest lead acid battery you can buy and it likely won't let you down or have a melt down like that expensive one will.

An oscilloscope could be used to visually identify a problem with a stator output, but not many people have access to one and know how to use it.

Then there is the possibility that you are simply drawing too many watts for the 1980's alternator. Did you add a whole bunch of resistors to make the LED lights work?

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TrialsRider

· #22 · 9 mo ago (Edited)

Josiah B said:
I've been told by numerous people, that if you disconnect the battery, the bike will still run.

and did you test that theory? Disconnect the battery and see what happens.

... what happens if your main fuse blows? My guess is the engine will stop.

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TrialsRider

· #23 · 9 mo ago (Edited)

Josiah B said:
... I thought the coils ran off the signal generator, and the battery just powered lights and accessories.

Signal generator signals the ignition when to fire, that is all it does. If your motorcycle had points and a condenser then it would not have a signal generator, the opening of the breaker points would initiate the spark.

You added LED turn signals, you didn't add more diodes to make the Light Emitting Diodes in those signals light, you added a load to the circuit so that there was limited forward bias voltage to your LED's. That load would be resistors or incandescent lamps not diodes. Diodes only conduct electric current in one direction, LED's are a special kind of diode that emits light when current is flowing in the forward direction.

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TrialsRider

· #24 · 9 mo ago

By the way, it's a Capacitor that makes a spark plug spark. If your engine has points and condenser it is the condenser that makes the spark because the condenser is a capacitor. If your engine has CDI that stands for Capacitor Discharge Ignition and it is still a capacitor that powers the spark coils.

A capacitor is a simple component that acts much like your lithium battery in that it can release or take on a huge amount of power very quickly. The signal generator tells the CDI when to dump the capacitors load into the ignition coils and the coils are just a transformer to increases the voltage from ~12 volts to several thousand volts making a spark at the plug gap, much like lightning. Reduced input voltage to the capacitor will result in reduced spark at the spark plug.

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