I think my signature line describes my bike pretty well.

I am having some issues with my battery being weak and the bike not starting.  I recently purchased a new battery, it is charged, has water and mostly works fine.  However, sometimes . . .

I checked the voltage at the battery 12.3 volts DC.  The SSM says I should have between 14 and 15 something.

I checked at the three yellow wires to the rectifier, I think I only have 40 volts AC.  (Meters confuse me a little, but I am reasonably certain I did this right.)  SSM says I shold have 100 volts AC.  My conclusion is the stator (generator?) is shot.

Can someone help my with this diagnosis?  Anything else I should try or check?  If that is the case, Bike Bandit wants almost $400 and I am thinking the bike is not worth that much, it is an '87 after all.  

Can I keep riding it and charge the battery (or get a tender to put on) every night?  

Thanks for any answers and input.

prechermike wrote on 09/28/11 at 08:26:29:



When you get the 12.3 volt reading is the engine not running?  If the engine IS running, at what rpm is it running when you get the reading?

Gyro and Dasch,

Yes the engine is running.  The SSM said to run the engine up to 5000 rpm.  I do not have a tach, but I had her thumping pretty good.  When I race the engine, the 12.3 volts at the battery does go up, but not to 14 volts.  I do not have enough hands to hold to the wires on the rectifier and run the throttle.  I guess I can get my son to race the engine, he would love that.

I am looking for 100 on the yellow wires, but the best I can get out of any combination of them is about 40.

Son has football game this evening, so probably no shop time today.  I will try that tomorrow, though and report back.  In the meantime, I will take other suggestions for the morning.

Thanks

prechermike wrote on 09/28/11 at 11:52:53:


On just about any charging system, you should be getting around 14.4 volts at 1000 rpm or so above idle.  It sounds like you have a problem.  This is surprising because Jap electronics are usually bulletproof.

Take the battery to town & have it tested.

Think about this for a second.

You are getting stator output at AC 70-80 volts.   A good regulator rectifier should be able to turn that into 14-15 volts DC with no issues whatsoever.

Go on Ebay and find a good cheap R/R with the correct number of wires (ours uses 5) off a Honda or another Suzuki bike -- some Suzuki R/Rs will even plug right in with the same connectors, but most will require you to cut and solder splice the wires.

Color of these R/R wires will vary, but there will always be 3 same color AC wires that can connect to any of the stator wires, and a + and a - DC lead that go to the battery.   Ebay always tells you what bike they came off of, and a little net search tells you what the output of the wires actually are.

Bigger, more powerful seven wire R/Rs have 3 same color AC stator wires, two same color separate + DC wires and two same color separate - DC wires that are intended to go to different modules on the bike (generally a modern sports bike has this) but these 2 plus wires can be put together into one general + and the 2 negative wires can be put together into one general - by simply splicing the wires together.

By doing these tricks you can always find a cheap R/R on Ebay that make your bike run again.

Your stator is old, your rotor magnet has likely weakened some over time, but 70-80 volts of output is PLENTY to charge your bike correctly through a fresh regulator rectifier.

PS -- clean your engine ground connection nice and bright and rig up a secondary engine ground or two from your battery terminal and one from your solder joint you make off the negative R/R joint -- ground corrosion is an ill that old bikes get that flat kills their black box electronics over time ....

I say this too because I had the same problem you did. Bike would run for a few days then eventually it would not start again. Battery would charge but I had a bad cell and not enough cranking power, bring to Autozone and get it tested, get that easy part out of the equation before you dig into charging system.

Being a shadetree mechanic, it's hard to know why we replace things and now it works.  W/o a scope and precision ohm readings on each coil, it's hard to know why your coil was bad.  Could have been a bad wire or connector.

Theoretically, 70 volts is enough.  but why is it different then the rest?  bad wire or corroded connector or some other singular point in the assembly.  A little resistance in the wrong place can be enough.