Cylinder 2 Runs Perfect! But Not The Others Why???

[br1amb]

Griffin

I will check them tomorrow morning.

Thanks again

[br1amb]

Coil voltage

Hi guys,

I know very little about electrical and that seems to be my problem.

Set ignition points to .018.
Zero fire at plugs
These are new points and before I used the feeler gauge I cleaned each feeler with lacquer thinner and wiped off feelers with towel so no oil from the feeler gauge would get on the points.

No fire at plugs.
Thought that maybe oil from the feeler gauge got onto the points and cleaned the points with lacquer thinner very carefully.

No fire at plugs
Grounded open points with a screw driver and there is spark at the points.

Coil 1 = cylinder 1 & 4
Coil 2 = cylinder 2 & 3

Key On
Coil 1 = 9.2 volts
Coil 2 = 9.2 volts

However I am currently charging the battery and there is 12.78 volts across battery posts

What voltage do i need at the coils? I am guessing 12volts.

Any ideas? Your help is appreciated.

[doctorgonzo]

I don't know if 9.2 is low enough to make you not fire, but search for "coil relay mod" and it will explain how to get that back to closer to 12 volts.

[br1amb]

I don't know if 9.2 is low enough to make you not fire, but search for "coil relay mod" and it will explain how to get that back to closer to 12 volts.

I have read the coil relay mod a while ago but thought it was more of a performance tip. I will look at it again.

Bike 79 GS750L

Voltage across fuses while grounding to battery terminal.
Fuse box is on the side of the battery

Voltage across battery = 12.10 volts
15A Main = 11.38 volts
10A HD Lights = 9.97 volts
10A Signal = 9.98 volts
10 A Ignition = 9.91 volts
Coil = 9.2 volts

I can't see any fire or feel any fire even when grounding spark plug. However the bike starts on 2 & 3 cylinders. As it runs on these too cylinders all the sudden cylinder 1 starts to sputter and then cylinder 4 starts to become alive. But 1 & 4 only come alive after 2 & 3 are hot.

New NGK spark plug ends tested out 4.9k - 5.0k
Coils ohm out

Any ideas?



I am grounding the plugs to the frame to the head bolts etc. once in a while you see spark but it's weak.

[Suzuki_Don]

First of all remove the spark plugs. Place a phillips screwdriver of the correct size in the end of the spark plug lead where it normally attaches to the spark plug. Hold the metal shank of the screwdriver 1/8th to a 1/4" from cylinder head fins and crank engine. You should get a good healthy spark. If you don't then that has eliminated the spark plugs from the problem. I would then swap the wiring on the coils from the points which in effect puts the other coil to 1 & 4. If 1 & 4 then run OK the problem is with the original coil on 1 & 4.
Hope this helps. Cheers. Don.

[br1amb]

First of all remove the spark plugs. Place a phillips screwdriver of the correct size in the end of the spark plug lead where it normally attaches to the spark plug. Hold the metal shank of the screwdriver 1/8th to a 1/4" from cylinder head fins and crank engine. You should get a good healthy spark. If you don't then that has eliminated the spark plugs from the problem. I would then swap the wiring on the coils from the points which in effect puts the other coil to 1 & 4. If 1 & 4 then run OK the problem is with the original coil on 1 & 4.
Hope this helps. Cheers. Don.

Thanks Suzuki_Don.

The connecting a screwdriver I get really weak fire. I am comparing to the fire from what you would see from 2 stroke snowmoble or a motorcycle with a cdi box.

I switched the black and white wires on the coils (black w White) and (white w black) and it wouldn't run at all. I spun it over more than 40 times and nothing. When i put the wires back to stock, (black w black) and (white with white). It started run up on 2 & 3. What does this mean?

[br1amb]

Did a compression test

cylinder 1 = 145#
cylinder 2 = 135#
cylinder 3 = 149#
cylinder 4 = 140#

At least that makes me feel better.

[catbed]

do the coil relay mod. 9.2 is waaaaaaaaaaaaaaay too low. it is considered a performance tip if your bikes runs well already.

[br1amb]

Thanks for your response. I am researching the coil relay mod right now. Not quite understanding it yet. What if i have 10 volts to the headlight. Is the relay mod covering up another problem?

[doctorgonzo]

Thanks for your response. I am researching the coil relay mod right now. Not quite understanding it yet. What if i have 10 volts to the headlight. Is the relay mod covering up another problem?

Well, to a degree yes. It's covering up that your wiring harness and the kills switch on the right handlebar are almost 30 years old and use crappy spade connectors. You bypass all that and run a hot straight from the battery to the coils.

[catbed]

Well, to a degree yes. It's covering up that your wiring harness and the kills switch on the right handlebar are almost 30 years old and use crappy spade connectors. You bypass all that and run a hot straight from the battery to the coils.

if you dont do the coil relay mod, you get a lot of voltage drop from old switches, old contacts, and 30 year old wiring. doctorgonzo is partially right. but, they are bad BULLET connectors that need to be replaced with SPADE connectors.

[doctorgonzo]

if you dont do the coil relay mod, you get a lot of voltage drop from old switches, old contacts, and 30 year old wiring. doctorgonzo is partially right. but, they are bad BULLET connectors that need to be replaced with SPADE connectors.

uuuuhhhhh.......
DUH!
Little tired here.

[br1amb]

Ok, now i feel stupid. Sorry guys, didn't mean to waste your time.

[n1elkyfan]

You don't get off that easy what was the final fix :-D

[br1amb]

Which side of the coil is the + side?

How do the coils know when to discharge. I have read many threads but something isn't clicking.