So here’s the deal. My 2007 CBR 1000RR started giving me charging issues. The battery was good, sitting at about 12.9 volts fully charged, but as soon as I hit the starter it would drop to around 10 volts and then only climb back to about 12.3 when running. Right away I knew it wasn’t charging like it should. I replaced the Battery after running a load test, load test showed it was week but still ok.
I started testing the stator. With the bike running, I checked AC voltage across the three yellow wires. Two of the legs were putting out right around 20 volts AC, but the third leg was only giving me about 3 volts. That was a red flag. I double-checked with an ohm test across the legs, and resistance came back within spec with no short to ground, which made it confusing because on paper the stator looked fine, but clearly it wasn’t.
Next I moved on to the rectifier/regulator. I hooked everything up, started the bike, and measured DC voltage at the battery side. Instead of getting the 13.5 to 14.5 volts you’re supposed to see, I was stuck around 12.2 to 12.3 volts. To rule it out, I swapped in a brand-new rectifier/regulator. Same results. That told me the rectifier wasn’t the culprit and the weak stator output was dragging the whole system down.
At that point I ordered a new stator, installed it, and ran all the same tests again. To my surprise, I got the exact same problem. Two legs strong, one leg weak. The bike still wasn’t charging. That’s when I realized the brand-new stator I bought was bad right out of the box.
At one point I removed the battery-side cable from the rectifier and tested DC voltage directly from the rectifier pin. That test gave me about 15.3 volts, which showed the rectifier itself was working and capable of producing the right output, but the system still wasn’t charging correctly once it was connected to the battery.
So after all that, I’m sitting here with a new rectifier, a new stator, and the exact same charging issue because the replacement part is junk. It’s been nothing but testing, swapping, and chasing my tail instead of riding.
After contacting the manufacture and trying to get a replacement they said no and will not replace it due to it passing the Ohm test, however failing the AC test.
I have a long list of emails to them, asking for a replacement and then finally said to just return it. They responded
Yes i should of not bought through this company. Not many Stators on the market for my bike, unless i want to spend $450
After fighting with two different stators and still having the same charging issue, I finally made the call that the only real way forward was to rewind the stator myself. At least that way I’d know exactly what I was working with instead of gambling on another questionable part.
I started looking into what it would take. I measured out the original windings and checked the gauge of the wire. Most guys recommend sticking with the same gauge or even going a step heavier for better cooling and durability, so I decided I’d use high-temp magnet wire, around 15-gauge, to keep resistance down and help it run cooler. The plan was to strip all the old windings off, clean the core up completely, and then rewind each pole by hand, counting out the turns carefully so everything stays balanced across all three phases.
On top of that, I’d need proper insulation such as fish paper or slot liner for each tooth and then finish it with high-temp epoxy or varnish to lock everything in place. That way it will hold up against heat and vibration once it is back in service. It is a little more work up front, but at least if I rewind it myself, I will know it was done right and I will not be stuck relying on another stator that might be junk before it even goes in the bike.
I am also going to take pictures along the way, showing each step of how I go about rewinding and rebuilding this stator. My goal is to make it better than factory, something that will last longer while running cooler, and to have a record of the process that I can share with others who might want to do the same.
I started testing the stator. With the bike running, I checked AC voltage across the three yellow wires. Two of the legs were putting out right around 20 volts AC, but the third leg was only giving me about 3 volts. That was a red flag. I double-checked with an ohm test across the legs, and resistance came back within spec with no short to ground, which made it confusing because on paper the stator looked fine, but clearly it wasn’t.
Next I moved on to the rectifier/regulator. I hooked everything up, started the bike, and measured DC voltage at the battery side. Instead of getting the 13.5 to 14.5 volts you’re supposed to see, I was stuck around 12.2 to 12.3 volts. To rule it out, I swapped in a brand-new rectifier/regulator. Same results. That told me the rectifier wasn’t the culprit and the weak stator output was dragging the whole system down.
At that point I ordered a new stator, installed it, and ran all the same tests again. To my surprise, I got the exact same problem. Two legs strong, one leg weak. The bike still wasn’t charging. That’s when I realized the brand-new stator I bought was bad right out of the box.
At one point I removed the battery-side cable from the rectifier and tested DC voltage directly from the rectifier pin. That test gave me about 15.3 volts, which showed the rectifier itself was working and capable of producing the right output, but the system still wasn’t charging correctly once it was connected to the battery.
So after all that, I’m sitting here with a new rectifier, a new stator, and the exact same charging issue because the replacement part is junk. It’s been nothing but testing, swapping, and chasing my tail instead of riding.
After contacting the manufacture and trying to get a replacement they said no and will not replace it due to it passing the Ohm test, however failing the AC test.
I have a long list of emails to them, asking for a replacement and then finally said to just return it. They responded
Yes i should of not bought through this company. Not many Stators on the market for my bike, unless i want to spend $450
After fighting with two different stators and still having the same charging issue, I finally made the call that the only real way forward was to rewind the stator myself. At least that way I’d know exactly what I was working with instead of gambling on another questionable part.
I started looking into what it would take. I measured out the original windings and checked the gauge of the wire. Most guys recommend sticking with the same gauge or even going a step heavier for better cooling and durability, so I decided I’d use high-temp magnet wire, around 15-gauge, to keep resistance down and help it run cooler. The plan was to strip all the old windings off, clean the core up completely, and then rewind each pole by hand, counting out the turns carefully so everything stays balanced across all three phases.
On top of that, I’d need proper insulation such as fish paper or slot liner for each tooth and then finish it with high-temp epoxy or varnish to lock everything in place. That way it will hold up against heat and vibration once it is back in service. It is a little more work up front, but at least if I rewind it myself, I will know it was done right and I will not be stuck relying on another stator that might be junk before it even goes in the bike.
I am also going to take pictures along the way, showing each step of how I go about rewinding and rebuilding this stator. My goal is to make it better than factory, something that will last longer while running cooler, and to have a record of the process that I can share with others who might want to do the same.
