93 VFR Voltage readings Bad = rough idle??????????????

My carbs are clean.  My tank/petcock are clean.  Knowing that...........

So, yesterday on my way home my '93 VFR started acting strange once warmed up.  The idle starting going bad/rough at stop lights and in traffic.  When I pulled away from a light or accelerated it ran as though it was starving for fuel until about 3K rpm at which point it ran fine on the highway all the way home.

This morning on my way to work same issue.  Started fine.  Warmed up fine.  First 50 miles of my drive it was fine.  Got to the gate on base and while waiting in line to get on base the idle got shitty and actually died once but started right back up.  Same thing on the way home.  Started fine but got the bad idle in traffic but fine above 3K rpm.

I just got home and though WTF!!!!!  I tested battery voltage while bike was off and its 12.1v

While ideling the voltage is at 11.8v

At 4500-5000 rpm it read between 9 - 12v

Am I to assume my R/R or stator as craped out and I should started searching through the 100000000 posts on here about it?

Check for burned connectors.  Pull the mid panel from the right side and check the plastic molex connector that connects the main wiring harness to the stator plug (3 yellow wires) also check the connection from the other end of the wiring harness where it plugs into the R/R itself (behind right rear panel).  If the connectors look ok then you want to test the stator (check resistance and continuity and also check AC voltage between yellow wires)   There are endless threads about this common issue but these are the basics.  If the R/R is original chances are it's toast.  The wiring harness is also a weak point so it wouldn't hurt to replace it if you haven't done so already.  Just keep in mind that R/R failures can often cause the stator damage so you may be talking about replacing several things.


Rollin

I pulled the stator plug (3 yellow wires) from the R/R and tested resistance as per the referances here and the stator checks out.

Would the R/R dying be the cause of the rough idle when hot?  I know with electronics,  before they die completely they can test/work good when cool but once they heat up they can loose resistance or other things.

My initial tests point to a bad/dying R/R so I think I'll start there and look into a new one with the vfrness.

Did you check the AC output at the 3 yellow stator wires?  What RPM is showing on the tach when at idle? BTW.....You should always conduct your testing with a fully charged battery


Rollin

I didn't check AC at the 3 yellow wires,  just resistance.  I assume while bike is idling,  red probe on yellow wire and black on ground?  Bare with me,  I'm no electrician.  RPM at idle is around 1100-1300 rpm.  I'll put the battery on the tender tonight.  I'm also going to look for a small voltmeter to hook up on my way home tonight from work so tomorrow while I'm troubleshooting I can see the voltage while riding.  Figure it is something all VFRs should have.

Dude - this is a straight up step by step test list for the charging debug.

As Rollin mentioned --go through all your connectors for burnt leads, dig deep. Crispy wires? Not good. Fix first!
Then---Go through this starting point quick list.  You will need a multimeter too.
Steps:
- Recharge battery overnite - then to take it to Autozone or similar to load test. -- Good? Bad? – An iffy battery can fake you out and act like a bad R/R. Buy new if needed.
- With good battery fire it up, warm up for a minute or two.
These are R/R quick checks---
--- With voltmeter at battery get voltages -- idle volts? 5000 rpm volts? What’s the numbers? Should be ~ 13ish min idle and in 14s at revs.
- Check stator
- 1. Pull connector apart. Set meter to resistance. Check pin to pin, 3 yellow wires, A to B, B to C, C to A. What’s  the numbers? 3 separate readings --Should be less than 1.0 ohms.  (Engine off)
- 2. Check continuity from each A,B,C pin to ground, -- -should be infinity - nada nothing. no continuity.  --   3 separate checks . (Engine off)
- 3. Crank it back up. Do another pin to pin thing, but set meter on AC volts. idle and 5000 rpms. What's da numbers? Should start 15 -20ish and climb 50ish and more.  Again – 3 readings
- Repeat hot.
This quick list will catch the obvious stuff, but if you need to dig deeper check this chart.
http://www.electrosport.com/media/pdf/fault-finding-diagram.pdf

Run the quick list tests and write down the numbers, tell us what you get, we'll go from there.

[image: View Post]mello dude, on 20 October 2012 - 09:06 PM, said:

Dude - this is a straight up step by step test list for the charging debug.

As Rollin mentioned --go through all your connectors for burnt leads, dig deep. Crispy wires? Not good. Fix first!
Then---Go through this starting point quick list.  You will need a multimeter too.
Steps:
- Recharge battery overnite - then to take it to Autozone or similar to load test. -- Good? Bad? – An iffy battery can fake you out and act like a bad R/R. Buy new if needed.
- With good battery fire it up, warm up for a minute or two.
These are R/R quick checks---
--- With voltmeter at battery get voltages -- idle volts? 5000 rpm volts? What’s the numbers? Should be ~ 13ish min idle and in 14s at revs.
- Check stator
- 1. Pull connector apart. Set meter to resistance. Check pin to pin, 3 yellow wires, A to B, B to C, C to A. What’s  the numbers? 3 separate readings --Should be less than 1.0 ohms.  (Engine off)
- 2. Check continuity from each A,B,C pin to ground, -- -should be infinity - nada nothing. no continuity.  --   3 separate checks . (Engine off)
- 3. Crank it back up. Do another pin to pin thing, but set meter on AC volts. idle and 5000 rpms. What's da numbers? Should start 15 -20ish and climb 50ish and more.  Again – 3 readings
- Repeat hot.
This quick list will catch the obvious stuff, but if you need to dig deeper check this chart.
http://www.electrosport.com/media/pdf/fault-finding-diagram.pdf

Run the tests and write down the numbers, tell us what you get, we'll go from there.

Awesome,  thanks for the step by step.  I appreciate it. Will have an update tomorrow.

Update:

Fully charged the battery overnight.  Brought it in to get tested and it tested fine.  Plugged it into the bike.  Let bike warm up.  Here are the readings:

Idle = 12.30V
5000 rpm = 13.40V  (it takes a few seconds to climb from 12.3v to the 13.4v and it kinda sits there.  Maybe will climb a lil higher if I hold it at 5Krpm longer.

Turn bike off.  Check resistance at 3 yellow wires.  A, B, C and back and forth and they all read 1ohms or less.  So that's good.

Turn bike back on and check ACV at 3 yellow wires.  Each read 20VAC at idle and 50VAC at 5000 rpm.

Aside from my DC readings at idle and at 5K rpms everything checks out.  Should I assume my R/R is weak and heading on it's way out?

another update.  Upon installing and testing an new fuel filter I found that my gas cap vent is clogged and won't allow a good stream of fuel.

How do you clean out a fuel tank vent in the cap?

^^^ Lean toward a bad R/R. ----While your at it check each pin to ground (Step 2) for shorts on the stator. Also sometimes its good cold, and bad hot.)


(Havent had to screw with a fuel tank vent.)