I recently had to replace the R/R unit on my CBR1000 and used a honda unit. The question I have is why the allowable charging voltage is so low. per the service manual it states 12.6-15 volts at 5000 RPM. I am reading 12.8 across the battery at 5000 so it appears to be in spec but barely. I left my DMM connected when I went for a ride and battery voltage varied from 12.3 at idle to 12.75 at 4500 which was freeway speed. All the othe bikes I own put out 13.5 to 14.5 and I believe it takes a little over 13 volts to overcome the batteries internal resistance for charging. Am I missing something? All connections from the stator to the R/R are clean and it checked out using the DMM. Thanks for your replies

 

If the battery was fully charged then the 12.8v you had on the terminals sounds ok, you would do damage(boil) the battery if you keep putting larger volts in an already charged battery.

 

Yes the battery was fully charged and is a fairly new unit. ( about 5 months old). Thanks for your reply

 

That's why you have a regulator. It turns excess voltage into heat......

I'd say you have a charging problem - anything under 13.5V at normal running speeds is a problem - I speak from experience on this
It's either the battery(which may have 12.8 volts but can't put out the AMPS required) or the regulator/rectifier is going. It could be the stator(alternator) but this is less likely unless you've run your battery dry and fried the regulator.

My own bike has an Electrex reg/rec (cheaper than the Honda one and charges at 13.5V at 1400 revs) and operating voltage is between 13.5-15.5V
and doesn't boil the battery.

used a honda unit - did you use one designed for the 1000F ? If not that could be part of your problem.

There are plenty of history threads on this subject.

 

When I stated it was a honda type unit it looked just like the fried unit I removed and was specified for my year and model bike but was not built by honda. I believe I got it from Ricks. I also felt the voltage should be higher then the 12.8. Anyone know why the honda servive manual allows it to be as low as 12.6?

 

You may have a charging problem originating at the stator, if all the rest is fine.
Check the wiring connections from the stator/alternator where they join in a plug behind the frame on the left side (red plug) and be sure all is in order.
You may also have a problem in the wiring loom between the stator/alternator and the regulator/rectifier.
I'd also check the output of that rec/rec - it should be way more than what you're getting. Check the manual for how to check the reg/rec.
Battery voltage should be around 12.6 when you've come back from a ride, with the engine OFF.

 

I did check the no load voltage with my DMM after the ride where I was monitoring voltage. It wasn't a very long ride approx 1/2 hour but the no load voltage at the end was 12.67 volts which meant the battery must not have given up too much charge. However that was a short ride. Also I don't have a connector between the stator and the wiring harness any more. The PO had removed that and installed spade type connectors in its place. I noticed they had gotten pretty hot at some point so I removed them and soldered the 3 yellow wires from the stator to the 3 yellow wires in the bikes wiring harness. No more signs of heating in that area now.

 

% 99.9 replaces the stator right SHADOW..

 

Battery sounds about right - mine has a similar no-load voltage after a ride.

No, Raiden, it could be the starter damper - there's an article on it.
If your electrical side has now checked out it's probably the starter damper, which, when it slips would sound as though the battery is flat. It's a small set of clutch plates on the end of the stator shaft.

http://www.stu.co.nz/cbr1000fix/

If this is how it sounds...........................

You can replace it with a new unit from www.mrcycles.com for about $220, or fix your old one.
Many of us (incl me) have done the job - Stu's article is GOLD

 

if the starter damper is the problem then the bike won't run .