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1986 VN750
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3,255 Posts
No, that is too low.

You want to see 13.5-14.5v @ 5k rpm. Check stator and r/r
 

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Premium Member
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1,803 Posts
No, that is too low.

You want to see 13.5-14.5v @ 5k rpm. Check stator and r/r
X2 You also want to see 12.5 - 12.8 at idle minimum.
 

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Discussion Starter #4
I charged the battery and cleaned the connection on the battery ground strap. After warming the bike up I still see around 12v while idling but when I bring it up to 5,000 RPM the voltage jumps to 12.5 and then slowly climbs to almost 14v in maybe 30 seconds and then bounces between 13.5 and 14. Is this normal? Is the regulator slow to react?

-Robert
 

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Premium Member
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1,803 Posts
That's fine.
Have to disagree. A battery that is putting out 12 volts is undercharged. Even showing 12.5 volts is low especially on our bikes. He should be getting close to 14 volts at 3000 rpms almost instantly, not 30 seconds at 5000. I would have the battery checked first, then check the rectifier.
 

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Discussion Starter #7
I should mention the battery puts out around 12.5 with the bike off. The battery is several years old now. I've heard it's not uncommon for our bikes to discharge at idle though.

-Robert
 

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1986 VN750
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3,255 Posts
I should mention the battery puts out around 12.5 with the bike off. The battery is several years old now. I've heard it's not uncommon for our bikes to discharge at idle though.

-Robert
Is the battery the "AGM" type?

If not, maybe it's time to upgrade to one.

If it is, 12.5 is too low of a 'charged' voltage for an AGM battery and it's probably toast.

If the charging system is healthy you shouldn't really discharge at idle, barely any charging sure, but it shouldn't eat the battery.
 

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FREEBIRDS MC CENTRAL NY
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16,080 Posts
I had a rectifier do that shortly before it died
 

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Discussion Starter #12
Is there a recommended brand of rectifier if I end up having to change it? I see one for $20 on Amazon that people say goes out after a couple weeks. Obviously not that one.

-Robert
 

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1986 VN750
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3,255 Posts
That kit works great. I bought my MOSFET separately and bought the wiring from them.
 
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