Dead Battery and engine performance

[gs750guy]

I jump started a severly dead battery on my '78 GS750 and got the bike to run but it ran ratty, was running on only three cylinders (as evidenced by a cold header pipe), the turn signals would light on the instrument panel but would not flash, and the headlight and instrument lights would dim or brighten depending on the RPM's of the engine. If it is not generating enough power to even flash the turn signals, is it possible that not enough power was available to spark all four cylinders?

I realize that power from the alternator powers the bike while it is running, but would a severly defective battery with some bad cells have some affect on the bikes performance?

A month ago when the bike had a good battery it ran and performed flawlessly.

Thanks,

GS780guy

[chef1366]

Yes
Especially with a poor charging system.

[Hoosier Daddy]

First step in diagnosis of many engine and electrical system issues is to verify battery is at full chage. The power generated by the electrical system is as all going to try and charge the dead battery.

[BassCliff]

Greetings and Salutations!!

Hi Mr. gs750guy,

The coils need a full 12 volts to fire a proper spark. Check your charging system and ensure you have a good battery. Clean ALL of the electrical connections and grounds. See the maintenance lists in your "mega-welcome" and check out the supporting documentation in the electrical section of my little website.

Let me dump a TON if information on you and share some GS lovin'.

I just stopped by to welcome you to the forum in my own, special way.

If there's anything you'd like to know about the Suzuki GS model bikes, and most others actually, you've come to the right place. There's a lot of knowledge and experience here in the community. Come on in and let me say "HOoooowwwDY!"....

Here is your very own magical, mystical, mythical, mind-expanding "mega-welcome". Please take notice of the "Top 10 Common Issues", "Top 15 Tips For GS Happiness", the Carb Cleanup Series, and the Stator Papers. All of these tasks must be addressed in order to have a safe, reliable machine. Now let me roll out the welcome mat for you...



Please click here for your mega-welcome, chock full of tips, suggestions, links to vendors, and other information. Then feel free to visit my little BikeCliff website where I've been collecting the wisdom of this generous community. Don't forget, we like pictures! Not you, your bike!

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BassCliff

[Normk]

If you are familiar with automotive, marine, heavy truck or similar charging systems you will have to unlearn some of the symptoms/causes which are familiar. Bike charging systems behave in some strange and (for me) unexplainable ways such as the effect a poor battery will often have on operation. If it were an automobile the effect would be a no start but not running problems.

I have several theories and could post them but someone will poke them full of holes. As an alternative, someone else could post them and I'll do the "hole poking".

A poor battery will load the system voltage down enough, as others have said, to cause the problems which you experience. You may have additional issues such as excessive voltage drop (line loss) between battery/alternator and coil positive, a weak coil, etc. any of which could exascerbate the problem but the first place to start is from a known good, fully charged battery. Many of us have tried to ignore this to our detriment.

If you need to trouble shoot before the battery can be recharged/replaced, you could use jumper cables from another battery such as an automotive one but do not have the automobile's engine running. Do not use a battery charger capable of more than about 5 amps. when the battery is connected to the bike's voltage regulator rectifier, in case the VRR regulates by shunting output to ground. may result.

[gs750guy]

If you are familiar with automotive, marine, heavy truck or similar charging systems you will have to unlearn some of the symptoms/causes which are familiar. Bike charging systems behave in some strange and (for me) unexplainable ways such as the effect a poor battery will often have on operation. If it were an automobile the effect would be a no start but not running problems.

I have several theories and could post them but someone will poke them full of holes. As an alternative, someone else could post them and I'll do the "hole poking".

A poor battery will load the system voltage down enough, as others have said, to cause the problems which you experience. You may have additional issues such as excessive voltage drop (line loss) between battery/alternator and coil positive, a weak coil, etc. any of which could exascerbate the problem but the first place to start is from a known good, fully charged battery. Many of us have tried to ignore this to our detriment.

If you need to trouble shoot before the battery can be recharged/replaced, you could use jumper cables from another battery such as an automotive one but do not have the automobile's engine running. Do not use a battery charger capable of more than about 5 amps. when the battery is connected to the bike's voltage regulator rectifier, in case the VRR regulates by shunting output to ground. may result.

Thanks for all of your advice and hardy welcomes.
Knowing that the battery is bad, I will take your advice and start first with the most obvious and go buy a fresh new battery and see what that does before going into panic state and possibly doing something stupid like chase symptoms around that may have been cured simply by replacing an old worn out battery.

I have a friend whose bike suddenly developed a miss like it was running on three cylinders. He then proceeded to panic mode......removed the carbs, tore them all a part and rebuilt them.....BIKE STILL HAD A MISS. He then spent money to replace the coils......BIKE STILL HAD A MISS. He then spent time and money replacing the points and condensers......BIKE STILL HAD A MISS. He then spent time and money replacing spark plugs and wires........BIKE STILL HAD A MISS. Ultimately, long story short, he discovered the problem was in a simple three dollar fuel filter that was plugged that he should have replace 35,000 miles ago.