Bike not charging after rewiring

[Erik K]

Hey everyone, I recently finished chopping my xs 400 into a chopper style bike and after an engine rebuild and everything else being modified including the wiring harness I have it running great however after about 15-20 min of running the battery will be dead. With it running a multimeter shows it running at about 12.5 volts and when I start to rev the engine it will drop down a little to about 12.2 volts. So definitely not charging. Before I messed with it I believe the charging system worked fine but I decided to simplify the harness by deleting everything that was not needed besides a headlight and tail light. Looking at the wires to the stator that do look very worn and beat but after testing these wires with a multimeter there appear to be no breaks throughout. One thing I may Beleive that I have done wrong is not creating grounds to the frame. I am not sure if this is wrong and I am sinning in the electrical world but where everything on the diagram says to be grounded I just ran to a singular negative wire that goes to the negative terminal on the battery. So every ground or negative wire all leads to one wire connected to the battery. Is this wrong? And is it required to be grounded to the frame if they are all in the end connected to the negative terminal?

 

[CaptChrome]

Theoretically the ground to the battery might be okay, but providing a ground to the frame is a good practice, regardless, and easy to do.

What sort of voltage regulator are you using?

 

[Erik K]

Theoretically the ground to the battery might be okay, but providing a ground to the frame is a good practice, regardless, and easy to do.

What sort of voltage regulator are you using?

Makes sense I will consider next time I build one. I am still using the stock original lovage regulator. However I did replace the rectifier with some random Yamaha atv one. Are they very specific on which ones they can use?

 

[CaptChrome]

The rectifier is just some diodes wired in a 3-phase bridge, so that should not matter and can be tested pretty easily. But first I would run a temporary jumper from the engine block to the battery negative and one from the frame to the battery negative and retry your test before drawing any conclusions.

The spark plugs ground to the engine block and the possible floating ground between the frame and engine might cause issues that will be hard to troubleshoot. Since the main thing you modified was the wiring harness grounding everything with jumpers will help rule that out.

 

[Erik K]

Alright I will try doing that. Is that what might result in my having no charge is just lack of grounds?

 

[CaptChrome]

The regulator needs a solid voltage measurement with respect to ground and this is a simple first step to troubleshooting. It may not be the cause. Next step is to buy a new regulator.

 

[Erik K]

Alright so I took the stator out removed all of the worn wires and reworked some brand new wires. I re assembled it and still nothing. So I went and got me the 80s dodge voltage regulator that people seem to have Luck with. Still nothing. I do notice when I sit and rev the engine it maybe goes up .5 volts so there’s gotta be something right? Even though it’s nothing really. What do I do now?

 

[tstidham]

There is also a field/excitor winding in the alternator that the regulator modulates ground to. I'll upload the diagram for 1978-79 models since I don't know which you have. You'll see the extra coil next to the alternator, that has a constant 12v on one side and the ground (bright green) is regulated by the regulator. Also, I also went with the cheap dodge regulator, but the first one I put in (ac delco gold) burned up in like two or three minutes, you could see a melted line in the epoxy underside. I then got a transpo brand heavy duty and adjustable model and have had great voltages ever since.