Voltage Drop at Coils?

[Mgriz]

Thanks to the help of you all here I have gotten my GS1000 back to running status (honed cylinders, rebuilt head, etc.). I had really weak spark when everything went back together so I went ahead and purchased a DYNA-S, Dyna 3Ohm coils, and Dyna wires. I installed them and it seems marginally better but it still sounds like its running rough and missing alot. I checked the ignition system and it turns out the colis are getting a little more than 8V, thats a whole lot of voltage drop and it has to be a problem right? I do have a full 12V+ at the battery. I would suspect the old wireing but I have checked the voltage at point C (12V to the DYNA-S) on my wireing diagram below and it is a full 12V, how can there be a 4V drop in 2 inches of wire? Or could it be the ground on the coils? What am I missing?

I also have a question about the timing... I dont have a continuity light so I set it using my multimeter and the following procedure.

1. Align the full advance mark (2nd mark to the left of TDC) for 1-4 w/ the timing mark
2. W/ multimeter leeds connected to battery ground and the black wire post on the 1-4 coil, rotate the magnet sleeve to the full advance position.
3. Adjust mounting plate so that the 1-4 coil is triggered when the sleeve reaches the full advance position (multimeter shows a jump from 1v-11v when triggered).
4. Repeat steps with the 2-3 coil.

This makes sense to me but I want to make sure this is how it should be, I need an extra set of hands to use the method DYNA has writen in their instructions. Thanks again for all of your help.

 

[Dink]

One corroded connector or one inch of corroded wire will easily drop four volts.
Dink

 

[SqDancerLynn1]

Check the orange/white ?? wire that feeds the fuse block should be at battery voltage another problem may be the ign switch itself - CHeck & make sure you have 12 0n both sides of the switch. If their is a problem ??? Consider running a relay use the orange/ wire to turn the relay on & run the 12V from the battery to the relay To the fuse block. Check your headlight It may have a low voltage too.

 

[RacingJake]

Battery power runs through the main fuse up to the key ignition switch then back down to the fuse box through the ignition fuse then back up to the kill switch on the handlebars then back down to the coils. If you have a bad connection at the Key ignition switch, fuse box, or kill switch that will cause a voltage drop.

I'd disconnect the wires to each coil then take another voltage reading. One lead on the hot wire to the coil and the other on the engine.

 

[duaneage]

TEMPORARILY run a wire from the + of the battery to the coils and try it. BTW you should have 13.2 - 14.4 volts when the engine is running above 2000 rpm.
Maybe your RR has gone south? Not an unusual problem for a GS.

 

[oldryder]

Voltage drop could be a bad ground for the coils. check that 1st. It can also be corrosion on switch contacts between the battery and the coils. A nice easy fix is to add a cheap relay (I used a $3 horn relay from NAPA) between the battery and the coils. Use the old low voltage wire to the coils to energize the relay. this keeps all the old interlocks operational. Run a wire from the battery to the relay contact, then other side of relay contact to coil. Good idea to put an in line fuse where you hook to battery. Have also seen people hook power take off lead to downstream side of main electrical fuse. either way you are bypassing all the contacts in the original circuit. A drop of 2 volts can cause problems, only 8 volts at the coils is guaranteed to be a problem.

 

[Mgriz]

OK, I have poked around and I've found that I have a full 12v all the way to the ring terminals on the orange wires. Thats where they conect via a screw to the DYNA coils. Now when I connect the ring terminals to the coils it goes back to 8v when I take a reading from the head of the screw. There is nothing between the various mating surfaces, the ring terminal and screw are in direct contact??? I have no idea whats going on with this. Thanks again for your help.

 

[earlfor]

If you have 12v on the orange/white wires when they are not connected to the coils and voltage on the wires drops to 8 volts when they are connected, then your battery is most likely ready for the trash can. a good battery should not drop 4 volts instantly like that. I will assume you are making no changes when checking voltage. Meaning, you cannot compare everything off on the bike, checking battery voltage then and turning the ignition on, headlight on, tail light on and checking voltage at the battery and expecting it to be the same. Remove all your fuses except for the ignition and compare voltages. If your battery truly is fully charged, a voltmeter should show about 13 volts at the battery terminals with the ignition switch off. I think though that a 4 volt drop in any case is a problem that must be addressed.
I would put the battery on a charger until it reaches a minimum of 13 volts and let the battery sit 24 hours. If it drops below about 12.8-12.9v, I would consider it toast.

Earl

OK, I have poked around and I've found that I have a full 12v all the way to the ring terminals on the orange wires. Thats where they conect via a screw to the DYNA coils. Now when I connect the ring terminals to the coils it goes back to 8v when I take a reading from the head of the screw. There is nothing between the various mating surfaces, the ring terminal and screw are in direct contact??? I have no idea whats going on with this. Thanks again for your help.

 

[BadBillyB]

The correct way to do a voltage drop test on a circuit is with the circuit energized. Heres how...Connect the red lead of your voltmeter to the battery + terminal. Connect the other lead to the B+ feed at the coil (with it connected to the coil). Now turn on the ignition and read the voltage on the meter. This is your voltage drop through the ignition circuit..........Poor connections (voltage drops) are best tested with a live circuit.....BadBillyB

 

[Mgriz]

If you have 12v on the orange/white wires when they are not connected to the coils and voltage on the wires drops to 8 volts when they are connected, then your battery is most likely ready for the trash can. a good battery should not drop 4 volts instantly like that. I will assume you are making no changes when checking voltage. Meaning, you cannot compare everything off on the bike, checking battery voltage then and turning the ignition on, headlight on, tail light on and checking voltage at the battery and expecting it to be the same. Remove all your fuses except for the ignition and compare voltages. If your battery truly is fully charged, a voltmeter should show about 13 volts at the battery terminals with the ignition switch off. I think though that a 4 volt drop in any case is a problem that must be addressed.
I would put the battery on a charger until it reaches a minimum of 13 volts and let the battery sit 24 hours. If it drops below about 12.8-12.9v, I would consider it toast.

Earl

Yes I am getting these readings with all else constant, everything off w/ the key turned to on and the kill switch in the run position.

I have done a little more troubleshooting, I get a 4v drop only when both coils are plugged in. If I unhook one of them I would get 12v at the coil that was hooked up. I couldn't figure out why this was happeneing so I decided to do the bypass/relay method some of you have recommended. All I need now is a relay, hopefully that will fix things...

But as you mentioned it could very well be the battery, which would stink b/c it is basically brand new. I bought it 4 months ago but the bike has been in various stages of repair since then and it has not had much use. II did fully charge it a couple days ago but ts on the charger now, we'll see how healthy it is. Thanks again.

 

[earlfor]

Are you saying you get no voltage drop with either coil if you check one coil at a time, but get 4 volts drop if both coils are connected?

Earl

I have done a little more troubleshooting, I get a 4v drop only when both coils are plugged in. If I unhook one of them I would get 12v at the coil that was hooked up. I couldn't figure out why this was happeneing so I decided to do the bypass/relay method some of you have recommended. All I need now is a relay, hopefully that will fix things...

 

[BadBillyB]

Did you do the voltage drop test/method exactly as I described ?? If you did, what were the results???........BadBillyB

 

[Mgriz]

Are you saying you get no voltage drop with either coil if you check one coil at a time, but get 4 volts drop if both coils are connected?

Earl

Thats correct.

Billy, no I have not gone out and used your method. I have been grounding the negtaive terminal of my multimeter and atatching the pos terminal to the point where I want the reading, then turning on the ignition. I'll give your method a shot tomorrow. Thanks again.

 

[RacingJake]

Where are you placing the neg lead when testing for 12 volts.

 

[RacingJake]

I just went out and tested my 2.2 coils and with a digital meter and the voltage would jump to 13.5 and then start to fall off too below 9 volts in a few seconds. Red lead on coil pos and neg lead grounded to the frame. Of course I'm using a msd MC2 box with the Dyna S ignition. Now if I remove the lead and wait a few seconds the voltage will go back up to 13 volts. Come to think of it it might just be a multimeter problem. Darn Murphy's at it again.

I'd say the coils are just being saturated since they are just like an inductor (load) waiting for the field to collapse.

So by my meter I'd say your ok, check your timing and move on to the carbs. You could always get a MSD box and really blast your coils. I'm wondering what the voltage would be if the engine was running, I'm to chicken to find out.

 

[Mgriz]

I have been groundng the neg leed by hooking it to the metal clutch lever on the clutch cover.

I'll finish the bypass/relay up tomorrow and play around a little more with measuring voltages. Thanks for going out and checking your system for me. I've double checked the timing and as long as Im doing that correctly its good. The carbs need to be synched but I'm not sure if that would be enough to make the bike sound like it does. If I get a chance I'll try and get a recording of it to see what you all think. It might sound normal, who knows, its been a while since I've heard it running right and I can't quite recall.

 

[Mgriz]

An update and some new questions...

I finished up the relay and ended up with less than 1v drop at the coils with everything hooked up. Using both the method I had ben using and the one that Billy posted. Seems to run a little better, but I still don't think it sounds right.

Now that the ignition system seems to be in order its time to move on to the carbs. The sytoms I have are as follows:

Unstable idle:
Idle raises to 2 or 3k rpm on its own, sometimes after being reved it will only return to 2-3rpm then slowly drop to 1100. I do not think it is the throttle cabling as I have held the throttle against the idle adjustment screw as it was fluctuating. I also checked the intake boots w/ the WD-40 method posted on this site and saw no results, I will try it again with a spray bottle and water just to be sure.

Backfiring:
If I bring the motor up to 3-4k rpm it starts loudly popping rapidly. I also get less violent backfiring on decel.

"Caughing" out carbs:
Occasionally at idle or under decel the carbs will make a "puuuuhhh" sound and the idle will drop.

3+4 lean:
Plugs 3 and 4 are greyish white in color after idling, 4 more so than 3. I'm thinking that this might be b/c the bike is on its sidestand but Im not sure.

I think thats about it, obviously it needs a carb synch but I want to see what you all think about all the issues and what might possibly be causing them.

Additionally, since this is my first rebuild Im a little tentative about riding the bike without everything being relatively perfect. But, I know that my compression won't be great until it gets broken in a little. Should I be okay riding this bike around in its current condition. I have ridden it around in 1st, it feels strong... no bogging or surging below 5k rpm. Thats a long post, sorry... thanks for your input.