View Full Version : Batt, R/R, or stator?

04-24-2010, 04:06 AM
I noticed on my VFR while it's running, the little digital clock jumps time randomly by hours at a time. Usually I've found on bikes that a small electrical glitch indicates some other big problem in the system that hasn't made itself known yet.

So I put a meter on the battery, and strange readings, at rest, engine off the batt read 13.6 volts.

Start the engine, and at normal idle volts to the batt are 14.70/72.

Increase engine speed, and the voltage starts to drop as the RPM's increase. For example at 2500 RPM, the Voltage was down to 14.2 then if you shut the bike off you can watch batt volts continually drop from something like 13.93, down to 13.6 or 13.5

I've never seen the charging rate go backwards like that though as RPM increases, and I think 14.7 volts charging is border on high, especially at normal idle. 1100/1200 RPM.

I know the R/R changes DC to AC and regulates voltage flow from stator to battery...

Off the top of anybody head, does this sound like a R/R issue or stator? Or could it be a battery on the edge of giving up?


Gas Man
04-24-2010, 07:37 AM
Can you unplug your R/R (also known as VR) from the stator?

You want to measure the AC voltage from the stator. Once you verify that is correct its easy to rule out.

Batt. How old is it? What kind?

R/R or VR is a hard one to troubleshoot. I find its easier to prove the others are bad or good. If all the other pieces check out, then it must be the VR.

I just did this process last summer/fall on a buds bike.

04-24-2010, 12:08 PM
Sounds like it's the stator running on 1 or 2 legs instead of all 3. Pretty much the identical issues I had with my Virago. Although it could also be the Reg/Rec. Without testing it, my money would be on the stator. I'd highly suggest a service manual an test them both out before buying either.

04-24-2010, 01:03 PM
I had the same thought about the stator doing that. I have some detailed testing steps now. (Am working on the manual for the bike)

I don't know too much about the battery yet. I have a new one of those coming already too as a matter of maintenance. I don't know anything about the existing batt, and I sort of assumed it lost at least some fluid when it went down.

I'm going out in a bit for more thorough testing and will post results.

Thanks for the replys.

04-24-2010, 05:18 PM
I'm following your train of thought GM, proving other parts bad/good. Stator checked ok including the ohm spec between any two of the legs, and none of the three are grounding out.

I don't know for certain how to check the R/R (yet) but somebody did take the time to mount a small computer fan on it to keep it cool.

The battery I can't tell how old it is, and while it's sealed I did manage to get a look inside of it, and found all the cells low/empty of any water.

So I'll wait for my new battery to show up, charge and install it, and test it all again with a good full battery and that should help narrow it down I think. Oh and making sure each connection is good...

Thanks again for the replies.

Gas Man
04-24-2010, 10:13 PM
Doug... consider buying an AGM battery instead of traditional liqued acid battery. They last longer and handle the vibrations of motorcycles better. You may cringe when I say this, but consider going to Harley and getting one that matches in size. Their AGM batteries are real nice. 1yr full replacement and 2nd year prorated warrenty. Further, I think the best selling point, if you ever need another or to warrenty it, you are never that far from a HD dealer regardless where you are in this country.

Gas Man
04-24-2010, 10:14 PM
Sounds like it's the stator running on 1 or 2 legs instead of all 3. Pretty much the identical issues I had with my Virago. Although it could also be the Reg/Rec. Without testing it, my money would be on the stator. I'd highly suggest a service manual an test them both out before buying either.
Not all stators are 3 phase. Some are just 2.

Doug... so the stator put out the proper AC voltage and increased with RPM?

04-25-2010, 01:16 PM
Yes, the stator is operating like it should. And the AGM batt is a good idea I'm also going to follow.

Just for grins I took some pics of my current R/R. Evidently this is not an uncommon "mod" to help keep them cool...

Gas Man
04-25-2010, 04:20 PM
That is interesting for the fan. Being its under the plastic fairing...I can see why.

Maybe that is why hd puts em up front in the open air.

04-26-2010, 07:53 AM
I vote r/r the stator seems to be putting out plenty on both high and low . it is the job of the r/r to pull it all together . you are going to cook that battery soon if you havent already

04-26-2010, 04:02 PM
After re-reading...I'm with snofrog on this one. 14.7 at idle is pretty f'ing high. Think it should cap out around 13.8 normally. I musta been 1/2 awake the first time I read this. LoL

04-26-2010, 04:58 PM
The batt is already "done". I have a new one on the way. I'm thinking about changing that R/R to a finned unit for better cooling, (and keeping the one in the pic for a spare).

On my other bike I moved it from under the battery box to behind the passenger foot peg so there's always airflow across it. Probably do the same on this bike.

05-01-2010, 09:30 PM
any news on this ?

05-02-2010, 07:56 AM
Put the new batt in, checked all the connections, cleaned and reconnected some that needed it, and the issue remains.

14.6/7 volts at idle, then as I rev the engine up, the volts go down. Still working "backwards" from how it should....

I'm going to change the R/R next, (soon), as the one thats on it appears to be stock, and the stock unit is very small and without cooling fins of any kind. There's also a wiring harness upgrade being made for these bikes that address the R/R issues I'll be adding at the same time.

I don't know what the hell Honda was thinking by using a non finned unit mounted behind plastic that gets minimal airflow airflow anyway, if at all. This unit gets hotter faster at idle than the R/R on my other bike.

Gas Man
05-03-2010, 10:19 PM
I would say yes its the VR/RR

05-04-2010, 10:56 AM
I should know soon. Just got a little sidetracked doing body work, and the tune-up/maintenance stuff.

Gotta love the first maintenance/once over on a recently purchased used bike. You get to see all the little things the PO did to keep it going. Some are pretty good ideas, some are very bad ideas, and almost all need to be un-done and then re-done....

My other bike actually came with home made air filters that were cut, glued, and shaped from scotch-bright pads. (among other WTF repairs)

Anyway, I'll post an update when the parts are in.