'85 FJ1100 - Turn Signals and Brake Lights affecting Idle

[wildpackets]

I had been having issues with an unstable idle since I put the bike on the road a month ago.  Ran some fuel system cleaner through it and it seemed much better but would still act up randomly when hot( at least I thought it was random).  A few days ago at a long red light I noticed that the idle was pulsing along with the turn signal.  Further experimentation showed that the idle became unstable with the use of brake lights too.  It is made even worse by combining the turn signals and the brake lights.

I would describe the unstable idle as a miss on one or two cylinders.  It is made progressively worse by adding electrical load through the use of the brake lights and turn signals.  The turn signals seem to have a more pronounced effect due to the intermittent load. Using both the turn signals and the brake lights at idle for a long red light will almost stall the bike. Turn off the turn signals and brake lights and the idle smooths out.  Problem does not occur when bike is first started, only after a good run...

Battery voltages look good. New Dekka battery installed by previous owner last season.
Looked for voltage drops across engine and frame grounds.  Seem fine so far.

Coil starting to fail??

Has anyone heard of this happening before?  I couldn't find anything in the forums.
I did see similar issues on some automobile sites but with no resolution.

Thanks

Craig

[FJmonkey]

Sounds like the crappy way the bike is wired. The coil relay mod may fix this. I did the relay mod and found it quite easy to do. No cutting of the original wires and you get full battery power to the coils. All you need is a 4 or 5 pin 30A VF4 relay, some crimp-on slip fit connectors and some 10AWG wire. I know it is posted here as that is how I learned how to complete the relay mod.

[Pat Conlon]

Check your ground and power wire to your igniter box.
The + side of this circuit runs through your run/off switch next to your throttle. Clean that switch. Of all the accessories your wiring system serves, you need good steady clean power at the igniter box the most. As monkey points out, you can always run a dedicated circuit and relay to power your coils....but the igniter box is fed off your oem harness.

It sounds like the power draw from your lights is causing a low voltage situation at the igniter.

You can try an experiment to confirm it's a low voltage issue at the igniter box.
Run a temporary jumper wire from the + battery directly to the igniter. Bypass the oem harness, switches and connectors. Read the wiring diagram in your owners manual, find out which wire provides power to the igniter. Don't cut this wire, just skin some insulation away from the conductors and tap in the temporary jumper wire.
Ride the bike.....See if the problem goes away....

HTH.  Pat

[Mark Olson]

make sure you are idling at 1100rpm. when it gets lower than that the turn signals and brake lights eat the voltage making the bike run rough.

[ct7088]

Use a relay to route the 12 volt supply around the ignition switch, you will cure the low voltage to the coil at idle. That made a huge difference on my 85.

Chris

[ribbert]

Electrical problems that present with those symptoms are nearly always earth related. There are exceptions of course but I would say 9 out of 10 are a grounding issue and you start with the negative terminal on the battery and work from there.

Noel

[ct7088]

Compare the voltage of the red wire(from the main 30 amp fuse) at the main switch connector to the voltage of the brown wire(out to electrical systems). I found 12.2 in to 10.0 out and occasionally dropping below 10 volts when operating the turn signal. Installing one relay cured the problem.

Chris

[wildpackets]

Sounds like the crappy way the bike is wired. The coil relay mod may fix this. I did the relay mod and found it quite easy to do. No cutting of the original wires and you get full battery power to the coils. All you need is a 4 or 5 pin 30A VF4 relay, some crimp-on slip fit connectors and some 10AWG wire. I know it is posted here as that is how I learned how to complete the relay mod.

Seems like this is something that needs to be done with these bikes.  I'll source the parts and give it a shot.  While I have it apart I'll check as many grounds/earths as I have access to.

I replaced the brake and some of the signal bulbs with LEDs and that made a difference but still not right.


When I get it done and tested I'll update the thread.

Thanks to everyone that replied

Craikg

[wildpackets]

Sounds like the crappy way the bike is wired. The coil relay mod may fix this. I did the relay mod and found it quite easy to do. No cutting of the original wires and you get full battery power to the coils. All you need is a 4 or 5 pin 30A VF4 relay, some crimp-on slip fit connectors and some 10AWG wire. I know it is posted here as that is how I learned how to complete the relay mod.

Seems like this is something that needs to be done with these bikes.  I'll source the parts and give it a shot.  While I have it apart I'll check as many grounds/earths as I have access to.

I replaced the brake and some of the signal bulbs with LEDs and that made a difference but still not right.


When I get it done and tested I'll update the thread.

Thanks to everyone that replied

Craig

Ok, had her apart yesterday and picked up a relay and a few other parts.  Here is what I found.

1) the voltage at the coils was good - Stayed over 12v at all times even with load and the bike not running.
2) A previous owner had done some re-wiring already and had replaced  the and relocated the fuse block - The voltage on the fuse block supply was low 11v down to almost 10v with load.

What I did.

Since the voltage at the coils was good I used the relay to run a new supply to the replacement fuse block.  Now getting over 12v at all times to the fused circuits.
Didn't like the look of the ground at the coils so I removed it and cleaned up the surfaces
I also turned the idle speed up a bit. Targeting 1100 but can't seem to get it to settle down.  Another issue for another day....

So, I guess the root cause of the issue was low voltage to the igniter.

However it could very easily have been (as suggested by the very helpful members)

1) Low voltage at the coils
Solution - Coil Relay Mod
http://www.fjowners.com/index.php?topic=15114.0

2) Bad Grounds - Igniter, Coils
3) Low Idle

Results:

1) The neutral indicator no longer dims when the turn signals are on
2) The bike seems to start better
3) The idle does not fluctuate with the turn signals
4) The bike does not run rough when electrical load is applied at idle
5) The bike seems to run better at all engine speeds

Just a great result overall!

Thanks again to all who replied..  I would have been struggling with this for some time if not for your suggestions.

Craig

[FJmonkey]

Very happy you fixed your voltage issue(s). Thanks for posting your solution, this will likely help others with similar problems. 

[fj1289]

I was a bit slow responding to this one - but low voltage to the igniter will definitely cause running problems.  In most cases I check the battery and spark plugs first.  I've had two different batteries lose cells before completely dying -- in both cases it caused a bad running problem at low rpm.  The ignition system definitely appreciates a good strong 12+ volts.

Good job hunting down the issue and THANKS for letting everyone know what you found