My '91 F2 has a strange voltage issue, it is not stable and fluctuates anywhere from 12.0 up to 14.2v while running. I have a Koso aftermarket digital dash that has a voltage reading on one of the display modes. Usually I will see it drop down to 12.5 when downshifting and coming to a stop. Sometimes sitting at a light, in gear with clutch lever pulled, it will drop down to 12.0v. Freeway speeds (70-80mph) usually hold at 13.8 up to 14v. I have replaced the stator, battery, and regulator rectifier all at the same time to be sure all those parts are new. Only other aftermarket accessories is LED headlight, LED rear turn signals. Not sure what the issue could be.

 

Could be loose wire to dash. Connect an independent voltmeter directly to battery and see what it says. I've got one on my bike since '86. Saved me quite a few times when it showed impending battery or RR failure.

 

I've got a few thoughts on this.

First, if you've got the volt gauge wired into the ignition circuit (so that it turns off with the ignition), you need to realize it's going to read about a .5 volts lower than battery.
This is normal. This is how I've got mine wired (for simplicity). Just need to be aware of that.

2nd, the stock F2 charging system doesn't put out much charge at idle. You'll mostly be reading just battery voltage, not charging volts.
If you've got aftermarket accessories or haven't ridden the bike in a while. It might be lower than you expect.
Or it could just be the battery going bad. New batteries can still go bad sometimes.

C), you said you replaced stuff, but you don't say what you replaced it with (most people don't).
And most people replace parts with junk aftermarket crap and they can be bad right out of the box. I've see it too many times.
Most notably is the reg/rec. If you bought a cheap one instead of the updated OEM one.
That's the first thing I'd remove and replace if there is a problem.

Finally, the stock system doesn't really start charging until around 1800-1900. Mine reads 12.2 at idle.
Then voltage will jump to 14.2 around 2000 rpm. As rpms rise toward 5000, voltage will then drop to around 13.5.
Above 5k, it's normally steady around 13.5.

And finally, (yeah I know) as long as it's consistently charging while at riding speeds, I'd guess that you don't really have a problem.
If the voltage is reading 10 something at idle after riding a while, then it's probably a bad cell in the battery.

 

I have a multimeter I can connect to the battery and check the voltage while I'm out to see what it's really doing. I will give that a try.

Thank Phil314 for the info, so on the Koso (DB02R) it's only got a few connections that I use out of it's harness: battery, ground, ignition, tach, coolant temp, and speed sensor. I can double check the power lead and see where it's connected, I'm positive it's not ran all the way to the battery. The battery is Honda Yuasa battery (YTX9 I believe), the stator and regulator reg is from Rick's Motorsport.

Seeing your voltage measurements I can see my bike is not too far off. I haven't seen idle drop below 12v on the display. I had the same Koso dash on my '98 SuperHawk 996 and I got used to seeing it from 13.8 to 14.4, however I know the CBR is different all together.

I will have to find an updated regulator rectifier to use and see if that changes thing, I think on the SuperHawk I had one from an 08/07 CBR600RR.

 

Rick's stuff should be good.
It's extremely rare for a stator to go bad.
Reg/rec go bad if you look at them sideway. Especially the original ones (in pic on right). Often they can take out the battery too.
I've fixed around 20 F2's with 'charging' problems since 91. New battery and new updated Honda reg/rec #31600-MV4-010 fixed all but 1.

 

Thanks for the part number, I will order it from Honda. Also I will double check my wire harness for any loose connections.