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Discussion Starter · #1 ·
I got my 2003 Yamaha R6 a few weeks ago and I ride it to and from work whenever it's nice and on the weekends. Recently I took it for a ride down the street to the gas station to fill up and then went to start and it was a sluggish start. Did it a couple more times and it still did it. Rode it home with no issues, put it in the shed, and read the manual for like 5-10 minutes. Went to start it again and it turned over 2 times slowly and didn't start.

Took off positive and negative wires to battery and put the charger on it for about 10 minutes then reconnected. Went to start it and it started right up. Battery has been checked by motorcycle shop and confirmed it is still good. Rectifier diode test confirmed that the diodes are good. Stator resistence is to spec and voltage looks good.

Is there any other reason that my battery would continue to slowly die? I disconnected my rectifier and it looks like some rubbery looking stuff was holding together the pins plugged into the rectifier. Can a spotty connection between the pins and rectifier diminish the sufficient amount of power my battery needs to stay charged so I don't have to charge it every so often? I'm looking to rewire the connection to the rectifier and actually install a plug for the pins to sit in. Any and all information would be helpful.

Thank you
:confused:
 

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My answer is by no means definitive, but my friend had the same problem. Swapped out the rec and stator and problem was solved.
 

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My XR eats my R6
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Start it and measure voltage, should be around 13.2v at idle and not exceed 13.8v when revved up. If voltage is less than 13.0v when revved then you have some resistance in your charging circuit (possibly loose connection) or like owazi said, stator or rectifier or both are bad. If charging voltage is good you have a small parasitic draw. google battery parasitic draw test.
 

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Discussion Starter · #4 ·
Well when I took the rectifier off instead of a plug it was 5 pins in the rectifier held by a mess of rubber. Was wondering if that stuff got on the connections could it diminish the amount of voltage supplied to the battery?
 

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My XR eats my R6
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Sounds like your wires melted

Read this thread or google R6 rectifier problem

Edit: My fault I thought you had an 02 not 03, so the rectifier problem shouldnt apply to your bike.

If you ride for a little while after a sluggish start does it fire right back up again immediately after as if your battery is fine? Or does only have a sluggish start after it sits for more than a few hours? Im telling you google parasitic draw test, very simple to do. And yes, high resistance at the plug can significantly reduce voltage output. you need to measure resistance of the actual wires going from the plug to the battery. If theres any resistance, calculate how much voltage is lost for whatever resistance you do find if any.
 

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Discussion Starter · #6 ·
It had the sluggish start when I was at the gas station. Started it a couple more times just to see if it did it again, which it did. Rode it home and it sounded fine. Got it in the shed and did something for 10 minutes. Tried to start it and it turned over twice then nothing. Didn't start. Charged the battery for 5-10 minutes then reconnected and tried again and it started.
 

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My XR eats my R6
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So its definitely not charging on its own unless your battery is toast ill bet your rectifier or stator or both are toast, or you have high resistance between the stator and the battery. You said everything ohms out ok so without knowing your exact readings compared to specs i cant give a definitive answer. Even if it barely started and you rode a mile or two, it would charge enough to give you a nice crank afterward if they were ok, again unless your battery is shot.
 

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Discussion Starter · #8 ·
Oh sorry. The stator plug resistance spec is 0.26-0.33 ohms. The number I was getting was 0.3 ohms. Voltage idled at 14v-15v and 50v at 5k.
 

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Discussion Starter · #9 ·
Spec voltage for stator is 14v, 300 watts at 5k rpm. My bike runs 8 amp hours so 300 watts translates to 37.5v
 

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My XR eats my R6
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Honestly im way too confused to try and help anymore at this point. I have no idea where you are getting 50v and 37.5v. If any modern bike runs over 15v it will overcharge and fry electonics, so your calculations are inccorect somewhere. And why are you including 8 amp hours? That is only how much power the battery can provide over time if the charging system completely fails. Has nothing to do with your probelm.
 

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My XR eats my R6
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My last guess would be you have a loose connection somwhere between your battery and starter, creating resistance and a slow crank.
 

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Discussion Starter · #13 ·
So I've replaced the battery and rectifier/regulator. We'll see how the charge holds up over the course of a week.
 
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