Low voltage when idling...

I'm hoping that some of you learned elders can share some insight here. My '97 VFR is having some starting/idling issues, but I'm 90% sure that they're electrical, and not the result of clogged carbs.

Bike history...

It has 11K miles on it. I bought it two years ago, with 6K on it. The PO barely rode it. It ran a *little* rough when I first got it, but after running a few treatments of Seafoam though it, it's been running great. Smooth, no hesitation, starts right up, etc. I do the Sta-bil thing in the winter, and run Seafoam though it about once year, just 'cuz. I also start it about 1x per month in the off-season.

It did have a bad R/R when I got it. The thing stranded me on my first ride with it. I replaced the R/R with one from a 2000 Yamaha R1. At that time, I also replaced the no-name battery with a Yuasa battery. I keep the bike on a tender over the winter, so this battery has never been dead. I know the battery is good. I also put a voltage meter on the handlebar, to keep an eye on the system.

After all that, I thought I had killed my electrical gremlin, but now I'm not so sure.


So here's my problem...

Symptom #1:

When I cold-start the bike (choke on) it idles a little rough and revs low (about 1000-1100 rpm) for the first minute. (Every now and then it will stall out and I'll have to restart it.) I've gotten into the (bad) habit of giving it a little gas as I start it. This seems to help. At first, the voltage will read pretty low, like 12.2V. Then slowly, after about a mintue, the revs climb up to 3000, the idle smoothes out, and the voltage rises to 14.0. After that, the bike runs fine and warmup proceeds normally.

BUT (and this is what makes me think it's not fuel-related) if the bike has been on a trickle-charger all night, it starts great. Idle is strong right away.


Symptom #2:

When I'm riding the bike and putting load on the engine, the voltage is doing great... consitently 13.8 - 14.0 Volts. But, when I stop at a red light, the voltage will slowly start to drop. It takes about a minute. 13.0... 12.8... 12.6... 12.4... 12.2... at around 12.0 the bike is starting to noticeably run rough and I start to worry that it might stall out on me. But if I take off, or even give it some gas, the voltage will shoot right back up into the 13+ range.



My theories:

Is this a stator output problem? At 11,700 miles?

Is this caused by the undersized 3-phase AC wires between the stator and the R/R? I've read that some people replace these with thicker 18ga wires.

Maybe it IS a carb problem? Some jet somewhere is cogged? (This is the worst possibility, because I DO NOT touch carbeurators. I know my limitations...)


Any ideas? Thanks for reading!

Rob

 

ALL bikes loose charge at idle ......while powering the headlight, ignition system, fuel pump, etc.

The service manual suggests and practice confirms that the battery does not recieve FULL charging voltage until 5000 rpms.

 

Whats your idle set at? It should even charge a little not much at an idle most engines need at least 13v+ to run on. yopur idle should be around 1200rpms give or take -+ 100rpms, lean more to the higher side if you're going to set the idle. Sounds to me like it's a week unit, I would go back with a Ricks RR made for the VFR , that and doublely make sure the spade contacts in the plug are clean and firm, this is one part to this problem that's over looked and the demise of a many RRs. When you watch the voltage when you start it up cold, yes the choke should pick up speed as it warms up, if left alone it will reach 4K, believe it or not this is normal, but you should see a spike to 14v+ right off the bat, once the battery starts being charged it will slowly go down in draw. even at idle mine is putting out 13.2-.5v It shouldn't take much voltage once warmed up like you where riding to and from you would see a quick spike to 14+v then it would settle down to the 13. something pretty quick. start looking at the RR and connections if this persists.

 

It sounds like the charging system is working as it should. I suspect that the battery is not holding a charge properly. The battery should be able to keep the bike running, while at low RPMs. It wouldn't be the first new, quality, battery to fail early.

As for the shot of gas on a cold start, I have always done this on non-FI bikes. I find that it makes for a quicker, cleaner start.

 

My experience with charging systems on my 96 says that at cold idle (around 1200) its going to idle at 12.2. So yes....if you are sitting at a traffic light, even though your bike is not charging, it is most likely maintaining a charge.

However once you give it a little gas, and get the revs up to even say 1500, that voltage should be up at 14v or even higher.

I have found with mine, that my voltage does not change much, once the revs get up to about 2000rpm. From about 1500 onwards all the way up to 5000, its sits right around 14.2 - 14.5.

I have been through many R/R's and pretty much have got it figured out that you need to keep your battery fresh, and keep a spare R/R under your seat.

 

^ Hey, where ya been? figured you would have something to say. huh..

 

Learned from the best!

Staying in Seattle this summer. Be ready to ride.

 

I'll second RVFR's advice.

I have to change my battery only after 2 years becasue it has a bad cell. If I keep it on the Battery tender it holds the charge, but once off and sitting, The battery only sits at 12.2 volts.

I'd charge your battery on the tender and once its charged, uplug it. In ten minutes take your mulit-meter and see how many volts the battery is at. 12.5-4 or under, she's bad. Also, when the bike is cold you can watch your mounted volt meter drop below 9.3 volts when you fire it up? Another sign you have a bad cell.

Hope this helps.

BZ

 

Nah, I'm pretty sure my battery is good. It'll stay at ~13.0 volts after being taken off the tender. And I've never seen it dip below ~11.5, even on cold start. I have a volt meter mounted on the right handlebar, so I have a pretty constant read on what's going on.

So... the consensus I'm getting is that there really isn't anything wrong... this is just how 4th Gen VFRs are. Hmm.

Are there upgraded stators that can be installed?

Has anyone here seen an improvement by up-sizing the AC wires between the stator and R/R?

 

I'd concur, sounds like things are fine then.

I have a Rick's Stator in the 97, but I don't know if it's any better than OEM.

BZ

 

tweek the idle up a bit, 11oo isn't bad but like Poweder says it' starts charging around 14-1500 till the 5k also on the cold start I I have it wher I'll start it on full choke no matter what first thing in the morning and let it go till she starts to run up then pull the choke like half off idling at 2000rpm where there's a plenty of charging going on. if not Hmm time to look into another RR good to have a spare anyway but do check the plug, what looks good may not be, it's a fussy little shit. don't ask how I know