Troubleshooting a "no spark" issue

[LongJohnny]

I have a 2002 Katana 750, and it will not fire at the spark plugs. I have searched to try to find a troubleshooting method to see how to find out where the problem is. The spark plugs are new, as I did this the first thing. The plug wires ohm out fine also.

What should I check, and how should I check it...

Ignition coil
CDI box
Anything else?

John

[Black_peter]

First off make sure you have good ground (from the plug to the bike)
What I do is wrap a big bare copper wire around the plug tight tight (so I have to unscrew the plug) then ground it to the coil mount bolt.
Second don't look for a big fat spark. So maybe shade the plug or check in the dark.
If you have an o-scope you can see the input voltage cycle on the coils. (also the output..)
There are some trouble shooting info here.
Try search again

[LongJohnny]

I tested the spark at the plug with an O-scope, and nothing but background noise. I am just wondering what kind of readings I should be getting from the coil, from the positive to negative terminal. I am assuming it is a resistive coil, or some sort of inductive load, but not sure.

John

[Black_peter]

I tested the spark at the plug with an O-scope, and nothing but background noise. I am just wondering what kind of readings I should be getting from the coil, from the positive to negative terminal. I am assuming it is a resistive coil, or some sort of inductive load, but not sure.

John

Wow..
I was kinda kidding about the o-scope..

OK here is the deal.. You have two coils.
A primary (where the CDI attaches) and a secondary (where the plug goes) One inside the other.
If you know enough to hook up an oscope than this will go fast (or slow )
The primary coil is charged with 12 volts then the CDI grounds it fast and hard. The 12 volts induced voltage into the secondary and the collapse discharges it. The secondary has many more winds of wire therefore some 2000 times the voltage (but just a bit of amperage) The high voltage jumps the gap of the plug. So to test the coil you need to make sure you are discharging the secondary. The best way is through the spark plug.
(back to making sure you have good ground) You can also make a tester with a nail set to the right gap. Look online for that, it should be out there.
Personally since you have access to the scope check out the primary first.
Just hook the two leads up to the scope as you would with any voltage source. Since its 12 volts it will be easy to find and it should crack often enough to see (while running the starter) or capture with the scope. If you want to check the secondary you have the issue of background (as you are at such a high voltage) and range, I'm not sure you can accurately calculate the output voltage well enough to get it in the right range to see it over the background however the attack and decay are high enough it should offer a good profile. Maybe there is something on the web about that. Another reason to not bother with the secondary is:
If the windings of the secondary are good
(30K to 40K ohms)
The plug wires are good.
Plugs are new.
The high tension section should be fine.
If you aren't reading any input voltage to the coils check the signal generator (magnetic sensor on the crank) under the tear shaped cover on the right side of the engine. It should read130 to 180 ohms.
(check the wires back to the CDI box too. Signal gen and coils)
Good luck..

[The CyberPoet]

If you aren't reading any input voltage to the coils check the signal generator (magnetic sensor on the crank) under the tear shaped cover on the right side of the engine. It should read130 to 180 ohms.

+1
If you've laid the bike down on the right side, odds are it is the wires from the signal generator being bad.

Other possibilities:

If the bike was laid down on the left side, or if you (or a previous owner) commonly used the sidestand as a pivot to rotate the bike around, odds are the safety interlock for the sidestand isn't seating right or the wires to it are damaged.

If the bike was disassembled or had a front-on accident, the 20-pin molex connectors above the headlight casing (under the front fairings) can prevent the bike from getting any spark if they aren't seated correctly. Open/clean/reseat.

If you haven't laid the bike down, but it was out in the rain for an extended period of time, I'd check/clean the handle-bar kill switch and the leads to the CDi for corrosion.

The safety interlock system may also be playing against you:
Clutch sensor switch: No continuity thru the switch = no starter engagement (spark should be unaffected)
Sidestand sensor switch: No continuity thru the switch + engine not in neutral = kills the spark
Transmission Neutral Sensor switch: see above
Run-switch (aka Kill switch) on the handlebar: no continuity = kills the spark.
There can also be an issue with the ignition switch and wiring leading to it, although usually a bike this new (4-5 years old) shouldn't have a problem unless someone actively damaged the wiring bundle or ignition key switch.

Good Luck!
=-= The CyberPoet

[Black_peter]

The safety interlock system may also be playing against you:
Clutch sensor switch: No continuity thru the switch = no starter engagement (spark should be unaffected)
Sidestand sensor switch: No continuity thru the switch + engine not in neutral = kills the spark
Transmission Neutral Sensor switch: see above
Run-switch (aka Kill switch) on the handlebar: no continuity = kills the spark.
There can also be an issue with the ignition switch and wiring leading to it, although usually a bike this new (4-5 years old) shouldn't have a problem unless someone actively damaged the wiring bundle or ignition key switch.

Good Luck!
=-= The CyberPoet

NOTE:
Just in case someone with a pre 98 comes across this:
Handle bar kill switch and sidestand kill the power to the starter switch as well as killing the spark.
So no sidestand or if the kill isn't in "run" then the starter will not run.
(I'm assuming this changed on newer models..)

[The CyberPoet]

NOTE:
Just in case someone with a pre 98 comes across this:
Handle bar kill switch and sidestand kill the power to the starter switch as well as killing the spark.
So no sidestand or if the kill isn't in "run" then the starter will not run.
(I'm assuming this changed on newer models..)

The kill switch still disables the starter. Sidestand switch doesn't, as long as the clutch sensor switch is activated.

Cheers,
=-= The CyberPoet

[Black_peter]

Ahh, 88-97 while there are some changes it's the neutral switch only that jumpers by side stand..

So
Clutch +Sidestand = start
Clutch +Neutral = start.

[The CyberPoet]

98+:
No clutch switch continuity = no starter engagement, neutral/gear selection irrelevant.

Cheers,
=-= The CyberPoet

[LongJohnny]

The bike is turning over, but there is not spark at the plugs. The side stand down, will disconnect the start, as does the kill switch, so there is no signal.

John

[Black_peter]

The bike is turning over, but there is not spark at the plugs. The side stand down, will disconnect the start, as does the kill switch, so there is no signal.

John

Looks like you're tracing wires then..
I'm guessing you didn't get any juice at the primaries?
Did you check the signal gen? If the resistance is good go head and try the handy o-scope on it, maybe the magnet isn't tripping it.
Did you trace the wires from signal gen to CDI?
From CDI to coils? Are the coils plugged in right?
I think you might have issues if they are not. I didn't think it mattered but I remember back a looooong time ago we decided it does..
Do a search. Spedee just posted a picture of the coil wire colors.

[LongJohnny]

What should the reading be at the signal generator? Should there be a resistance between the two lugs?

John

[Black_peter]

The resistance of the signal gen is 130 to 180 ohm.
I'm pretty sure it is part of the 12 volt circuit if you want to try and read the change in voltage as the magnet sweeps..

[JIMMYD]

No Spark

The resistance of the signal gen is 130 to 180 ohm.
I'm pretty sure it is part of the 12 volt circuit if you want to try and read the change in voltage as the magnet sweeps..

Hey Fellas

I have about 10 or 11 volts at 1 coil primary side and something like 2 volts at the other coil primary side.

This is an obvious problem............ but what could cause this problem?

Coils and wires all ohm out with expected values.

If I'm not getting proper voltage, then I obviously won't get proper spark.