RPMs only increase with Headlights on.

[txt0080]

I recently aqcuired a 79 gs425. I was able to start the bike on the first or secord kick after rebuilting the carbs. Funny thing is, if the headlights are off, it will only idle. I cannot get it to rev past 1000 rpms, it just sputters when I give it gas. But as soon as I turn the headlights on, it will rev right up. It seems to run perfect with the high beams on and the brake lights on. Being new to the GS bikes, is this a normal response of a 79 GS425. Thanks in advance for any help.

[trippivot]

after april of 1977 ALL motorcycles in sold America cannot turn the lights off unless someone has modified the wiring.

Do you have a American bike or are you somewhere else?

if the lighting circut has been modified I would go directly to the spot where the circut interrupt is located and begin the diagnosis there.

I am used to the exact opposite symptoms=lights on and no revs.
bad battery or charging system.

But this is a strange one I am curious about.

[txt0080]

I in the the great state of NJ... but anyway, I do have a factory headlight switch which I can turn on and off. It's not easy to turn off, I do have to lift the switch up a little to side it to the off position. I don't believe anything was modified with the circut, everything looks stock.

As for your problem, how old is our battery?

[txt0080]

I should also mention, that it's not just the headlight that cause the bike to run proper. If I have the headlight off and engage the brake light, the bike to start to run normal. I don't understand.

[Dave8338]

I would clean all your connectors very well and reinstall with some dielectric grease...great stuff! Pay special attention to the grounds, all of them...as they are also critical to the equation. It sounds like a poor ground issue and that once a high draw device ie. head or brake light is applied, the current is finding it's way through the circuit.

My guess is a bad ground or series there of. Good luck. Keep us posted.

[Steve]

I recently aqcuired a 79 gs425. I was able to start the bike on the first or secord kick after rebuilting the carbs. Funny thing is, if the headlights are off, it will only idle. I cannot get it to rev past 1000 rpms, it just sputters when I give it gas. But as soon as I turn the headlights on, it will rev right up. It seems to run perfect with the high beams on and the brake lights on. Being new to the GS bikes, is this a normal response of a 79 GS425. Thanks in advance for any help.

First off, congrats on the "new" bike, and welcome to the forum. \\/
BassCliff will be here momentarily with the "official" welcome.

Now, to your problem...
Suzuki disabled your headlight switch, but somebody has re-enabled it. No matter. The charging system includes a stator that has three windings. One of those windings is switched by a second set of terminals on the headlight switch. This is to prevent overloading the regulator/rectifier when the lights are off. Apparently, one of the other windings has failed, leaving only marginal capacity (1 out of 3 windings) when the lights are turned off. When you turn the lights on, a second set of windings comes into play, giving it plenty of juice.

First, make sure all the connections from the stator to the r/r are clean and tight. If that does not help, follow the troubleshooting procedure in the Stator Papers in the Garage Section of this forum (note the link I just gave you). You may have a bad stator, but it might also just be bad connections, which these bikes are famous for.

Good luck, happy hunting. Let us know what you find.


.

[BassCliff]

Hey howdy hey!

Sorry I'm late! :-D

Mr. txt0080,

Let it be known that on this day your are cordially and formally welcomed to the GSR Forum as a Junior Member in good standing with all the rights and privileges thereof. Please note that "good standing" implies pictures! :-D

Sometimes the electrics on these classic bikes have been modified by the PO. That can make troubleshooting even harder than a completely stock system. I'm just now getting to know the electrical system on my bike. I'm going through all the wiring, cleaning/replacing connections and making sure all the ground connections are clean. I'll be replacing my r/r as soon as it arrives. The good folks here are teaching me to be a better motorcycle mechanic and a better motorcycle rider. Thanks for joining us.

Thank you for your indulgence,

BassCliff
(The unofficial GSR greeter)

[IanFrancisco]

Headlight switch

I in the the great state of NJ... but anyway, I do have a factory headlight switch which I can turn on and off. It's not easy to turn off, I do have to lift the switch up a little to side it to the off position. I don't believe anything was modified with the circut, everything looks stock.

My 1980 GS450S also has a factory headlight switch. One point to remember is that one leg of the stator is switched off by the headlight switch, ie, lights off = a 2 phase alternator and lights on = 3 phase. Interestingly, looking at BassCliff's wiring diagram and harness for the charging system also shows the wire routing still in place for this despite the fact his bike has no headlight switch. 1980 GS850GT. Most people just route the three stator wires directly to the Regulator/Rectifier. Some cut out the connectors and solder the wires together. Not a bad idea. Also while you're sorting your electrical gremlins it would be a good idea to go through the harness and clean every connection you can find, and run a separate ground wire directly from the RR negative (usually black) to the battery neg. pole.

If you're sure your wiring harness is unmolested, I would do the above mod, to route all three stator wires directly to the RR. If you have a good non-Suzuki or aftermarket RR it will handle the full output from the stator with no problem, and if you don't do a lot of highway riding you'll need the full output of the stator to maintain the charge in the battery.

Many posts have mentioned a Honda regulator is a good choice for upgrading. On the VX800 list I read, one guy has used a RR from a Harley V-Rod. The Harley alternator puts out 280 watts so that RR is completely unstressed by the output of any stator a Suzuki can use. Probably overkill, but it would be the last RR you'd ever need to buy for a GS.

ian

[BlackStar]

[quote=trippivot;700520]after april of 1977 ALL motorcycles in sold America cannot turn the lights off unless someone has modified the wiring.

My 1978 GS1000 sold new on April 14 1978 in Indiana has a functional headlight on /off switch. I'm the 2nd owner, my Uncle was the 1st, and it has not been modified. Perhaps Suzuki was non-compliant for a period of time.

[Steve]

after april of 1977 ALL motorcycles in sold America cannot turn the lights off unless someone has modified the wiring.

Yes and no. :shock:

Yes, there was a cut-off point, but I don't think it was April, 1977. Many manufacturers started wiring bikes so the headlight was always ON. I had a '76 KZ400 that had a delay device that lit the headlight after it sensed more than battery voltage (then engine had to be running and charging the battery). My '77 KZ650's light was always ON with the ignition key. My '79 KZ1300's light would cut out when the starter was pressed.

California had a law requiring any bike first sold and registered on or after January 1, 1978 to have headlights that were ON whenever the engine was running. I was under the impression that the Federal requirement kicked in on January 1, 1979.

Why did Suzuki tend to hang on longer? I don't really know. My son had an '81 450 that had a switch, but was blocked at the factory so it would not turn OFF. Easy enough to remove the block. It was probably easier for Suzuki to just install the block for the US market and leave it off for the rest of the world. Certainly cheaper than tooling up two separate assemblies. As the rest of the world adopted something close to our standards, they phased out the headlight switch and now we don't have them.


.

[txt0080]

Thanks for all the information. I start looking at the stator tomorrow. As for the headlight, I believe Suzuki just put a block on the switch. The block must have been removed, because I can just lift the switch a little and pull back to turn off the lights. Thanks again