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Too low a voltage going to 1 coil.

  • Thread starter Thread starter robinjo
  • Start date Start date
R

robinjo

Guest
Doing a little work on the old bike between Christmas festivities and tried out my new multimeter. With the ignition turned on the left coil gets 12.1 volts but the right one gets about 10.2 (10.4 after some contact cleaning) I traced the wire back to the black ignition box, a sort of amplifier according to my manual and right where the wire leaves the box it's also shows that voltage.

Spark on the 2 inner cylinders is weaker but blue, can't cross 5mm gap,
outer ones about 8 to 10mm.
Bike has a brand new battery reading 12.7 volts.

Where do I go from here :?:
 
Swap the coils and see what happens. My guess is that the coil with the lower voltage is the problem.
The ignition box is either working or it's not; nothing in between (as far as I know).
 
check and clean all your connections for the coils, the coils get power from the ignition switch via the kill switch, the black igniter box controls the ground side, not the positive.

with the igniter box disconnected, set your new meter to resistance, with the ground lead on the terminal for the black with white stripe wire, contact the positive terminal of the meter to, first the terminal for the igniter with the white wire, then the terminal for the yellow with a black stripe wire.
you should get no conductivity or extremely high resistance.

with the bike running see what the voltage reading is on the orange with white stripe wire at the coils.
 
Thats what you get for testing things..worry!!!

Besides that, check all the connections. I put a relay in mine to bypass the kill switch, which now only works to turn the relay on and off. And the relay to bypass the ignition switch...
 
saaz said:
Thats what you get for testing things..worry!!!

Besides that, check all the connections. I put a relay in mine to bypass the kill switch, which now only works to turn the relay on and off. And the relay to bypass the ignition switch...
Click to expand...

Yeah you're right about the worry part LOL

I know I shouldn't have started with those funny colored wires that run all over the bike for some reason, I get a shock just looking at the wiring schematic...I'm contemplating wimping out and take it to the bikeshop 8O this stuff is just not for me I think :oops: even with the great help from the members of the good site, it's my shortcoming/fobia. Give me pistons and bearings and chains and stuff, things that I can see moving and I'm a happy guy. now lets see what's left of the christmas bonus...
 
i have a thought 8O 8O 8O .
check the ohms of the primary side of each coil just for starters and then check any lug from the primary winding to each one of the spark plug wires to see if there is even a very slight leakage. there should be an infinite reading as only inductance couple the primary and secondary side.
I would even perform the test from each lug on the primary winding. It sounds like a low grade short somewhere.
Since the ignitor completes the ground to get the coil to fire, i dont doubt that it is even possible for one of the transistors in the ignitor box to be leaking. Someone with more knowledge will have to speculate in that area. maybe a test rom each 12 volt line on the ignitor to its respective ground wire could show a diference in resistance. or possibly show a current flow when voltage is applied.??????
 
RIGHT! here I am with some more test results...

Did some resistance tests on the "weak" coil:

Between the + & - tabs 4.5 Ohm
Between the 2 plug caps 21.6 Ohm
Between the 2 HT leads without the plug caps on them 11.8 Ohm
Plug cap 1, 5.0 Ohm
Plug cap 2, 4.8 Ohm

Then I did some testing on the "good" coil

Between the + & - tabs 4.5 Ohm
Between the 2 plug caps 24.7 Ohm
Between the 2 HT leads without the plug caps on them 14.8 Ohm
Plug cap 1, 4.9 Ohm
Plug cap 2, 4.9 Ohm

Dom there is no continuance from the lugs to the wire ends measured.

According to this:

Primary resistance

Now unclip the black and white wires from you coils. Set your meter to 200 ohms. (its the scale with the little horseshoe looking symbol) Leave the ignition off. The orange/white leads to the coils will also be disconnected. Place the black probe from the meter on one of the tabs/connectors on the end of the coil, Place the red lead on the other. (it does not matter which lead goes to which tab) Any reading between 2 and 5 ohms is within normal service limits. You will probably get a reading close

Secondary resistance

Set your meter to 200K on the ohm scale (the little horseshoe again )
Ignition still off and you can leave the previous wires on the ends of the coils still disconnected. Pull the spark plug wires/leads off of cylinders 1 and 4. Insert the black probe of the meter inside the spark plug cap of cylinder 1 to touch the round metal ring that normally snaps onto the spark plug top. Insert the red probe inside the lead/cap for cylinder 4.
It does not matter which probe goes to 1 and which probe goes to 4.
You should get a reading between 30K to 50K ohms.
Click to expand...
piece by Earlfor both my coils have to low a secundairy resistance although the "weak" one even lower then the "good" one.

Does this mean I need 2 new coils? :? The weak ones looks stock and old, the other one looks brand new.

And yes this is probably the longest time between updates in a technical post! :lol:
 
Older coils do loose their zap after a few years. I just replace my original coils, and it made a big difference to idle performance and cleaner runing (well, it will be better when I properly tune the bike! The power wire to the coils should split off from the same source, so do you get the same voltage reading when the power wire is disconnected from the coils?

I am a bit wary of the coil eventually failing, as this grounds out the power wire in most cases and burns something out. I just replaced a darlington transformer in my elecronic ignition because a coil failure overloded it. If the coils are on the way out this may also happen. I was lucky I could replace mine myself for A$10

And if you want to know it was one of my replacement GSX-R coils I put in recentlythat went, not one of my crappy old coils!!!
 
saaz said:
The power wire to the coils should split off from the same source, so do you get the same voltage reading when the power wire is disconnected from the coils?
Click to expand...

I just measured the power wires off the coils and I get 11.65 on both, the bike hasnt been ridden in weeks and there has been lots of testing and starting so the battery is low. So it's not a bad continuance in one wire I think :-k

I think I'm gonna hunt down some good coils now...
 
Would coils of a GSX600F Katana work?

8902.jpg
 
Robin, I KNOW what your going through bro, but I learned from the great Earlfor. And I was able to FIX my bike :)

You said your getting 12 V on the left coil and 10 on the right. I had the same problem.

And now that I have it all "fixed" Im not too sure thats a problem after all. I had like 12 v on the left coil and 11 on the right.

I noticed I got the exact same reading when the negitive wire going to the coils was not connected. Remove both the Positive and negitive wires leading to your Left side coil, test the positive, you prolly get around 12 V depending on how charged your battery is.

Now remove the both the positive and negitive leading to the right coil. Test the positive wire, I bet you get the same reading as the left.. now connect the negitive wire, did the voltage go down? Let me know..
 
Robin, sorry dude I had written that like 2 days ago and just now clicked send haha. I think the Coils you mentioned would work. I had around the same voltage reading as you when I tested both coils while they were connected. I had the correct amount of voltage leading to the coils but the coils werent doing there job.

As long as you have a way to connect those coils they should work. I have a 82 gs650 and was able to use the coils off of a 79 550. Totally different wire connecters but I MADE it work with PC part connectors, like you plug a powersupply into a CD drive :P

My problem was the coils were grounding out inturnally.

Hope it works out for you.
Justin
 
hi, i have 3.9 ohms on RH coil and 4.0 or 4.1 on LH coil

is this good ?

80 gs450L thats having raw fuel soaked RH spark plug problem lately last couple days out of the blue for no reason


i just checked spark condition with using the plug that wasnt soaked and both coils cause a nite bunch or white sparks snap snap snap very audible, soooo.......

humm,

im stumped,

getting a wet plug and with great spark, but then inever checked spark before i went and cleaned all 12v connections with WD40, also i have a bunch of dielectric grease i will use if i have to!

thanks
 
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