Topic: Rebuilt Harness - Problem #2 - Ignition - No Spark anywhere

[750goes]

I told you I would annoy you all..
A successful morning with problem #1 fixed.

Now progressing to the ignition circuit

I have cleaned all the wiring contacts, made sure I have a good Earth, and have found that I have no spark at all at either the
points, or at the spark plugs.

I feel the problem may be in the switch housing - it is not an original but has all the necessary coloured wires coming from it.

I have tested the black power lead going into the switch and the black/white coming out to the coils -
I have continuity through the switch..
I have continuity of the black/white coil wire from the handlebar switch to the coils..
I have continuity across the coils in both directions however I attach the multimeter probes.
I have continuity from the yellow coil lead through to the yellow on the points plate, same for the blue wire.

I took measurements of the resistance at the coils and plug leads results as follows:

Yellow coil lead to black white - scale 200 - reading - 5.6ohms
Blue coil lead to black white - scale 200 - reading - 5.0 ohms

Plug leads without caps 1 & 4 - scale - 20k - reading 14.44
Coil stamped with FL703-12V96F - TEK
Plug leads withount caps 2 & 3 - scale - 20k - reading 14.43
Coil Stamped with FL703-12V96E - TEK

Oh yeah - this is with the ignition in the OFF position

Any thoughts ?? or do I need to give more information....

thanks for the replies in advance

[scunny]

with ignition on, do you have power(12 volts +) at the coils and at the points ?

[750goes]

I don't think so, as I shorted across the points with a screwdriver with the ignition ON and got no spark that I could see.

[scunny]

you will only get a spark with the points open I think. but if the set up on a 650 is the same as a 750, your next point of call back toward tha battery is your kill switch, black and white going to the points and coils

[750goes]

I'm not sure if I checked the power side of things, I got a bit engrossed in all these wonderful OHM readings.

I will check the power to the switch tomorrow - but I think it was showing voltage similar to what I had across the battery terminals.

can you confirm - with ignition ON
I should check for voltage from ignition switch to handlebar switch - same as across battery?
black wire into switch to the black/white wire out of the switch (to coils) - same as acorss battery ?
then also check when I turn the kill switch to OFF there should be no voltage from the kill switch to the coils ?

I'm have to make another 12V test light, as the one I have been using is not really working properly.

any issues with the resistance readings I have shown for the coils and plug leads??

I wish this was as easy as undoing bolts..

thanks again 

[scunny]

yes, you should have power to the kill switch and going away to coils and points, turn kill switch to offand power going out on the black/white wire should disappear.( power measured between wire and earth) I hope this helps, electrical must be done logically to simplify it

[750goes]

Yes I know

I'm pretty simple when it comes to electrics... thanks and will reply when I have some better results (I hope).

 

[scunny]

good luck, I believe in karma and will be asking questions myself when I try and reassemble my bike. I forgot how many bits make up a motorcycle 

[Jonesy]

Let's take a tour through the ignition system-

Starting at the battery, we go through the main fuse through a heavy red wire to the ignition switch. When this switch is in the ON position, the black wire, or main power buss, is connected to the red wire and powers up the bike. The black wire goes up to the kill switch on the right-hand control pod (through a bullet connector in the headlight bucket). When this switch is in the RUN position, the black wire is connected to the black wire with a white stripe. The white stripe wire runs back to the coils (again, stopping for a bullet connector in the headlight along the way), where it is split with a double bullet connector to feed positive battery voltage to both coils. This takes care of the positive side of the system.

Now to complete the circuit we take a look at the ground. Each coil has a wire (yellow or blue) that attaches to the harness via a bullet connector at the coil. These wires attach to a sub-harness on the engine near the right-hand side of the air filter case via more bullet connectors and the harness will be strapped to the frame rail. The wires finally end up at the breaker points, where when the points are closed, the circuit is completed to ground. When the points break, the primary current is cut off, the magnetic field in the coil collapses and induces a charge in the secondary coils, and you get a spark.

Your coils sound fine. They are usually bulletproof on these bikes.

So, after looking at the whole picture,
-Do you have battery voltage at the coils with the key on and the kill switch on? (If not, look for broken wires or dirty bullet connectors or bad switches.)
-If you have voltage to the coils, Do the points make/break continuity at ground? (If not, check for shorted wires, which can happen if the engine was re-installed and the wires to the point were pinched on the frame, dirty connections, shorted condensers, bad points).

If yes to both of the above, check the plug caps. If they measure out of this world on resistance, replace them. They are easy to get and in my opinion, cheap insurance. Also, when checking for spark, keep in mind this is a "wasted spark" system, so plugs 1-4 and 2-3 have to be grounded together in order for it to work.

Let us know what happens.

[750goes]

Jonesy - you are now a TRUE GURU....

Well I traced my power (+) from the ignition to the kill switch - all OK
tracing power (+) from the switch was a pain beacuse it did not happen

Just mentioning again I do not have an original switch...Opened up the switch - and this is what I discovered.
The OFF/RUN/OFF switch has two wires attached to it - being BLACK/WHITE (coil output) and GREEN (I still have this hooked up to EARTH).the Starter button has the Red/yellow
the Light button/switch has brown/blue, BLACK, another colour - forgot.
ALSO hanging out the front of the switch is another short black wire and a green/yellow wire - I think these are for the front brake switch.

Anyway to the point of being dumb I discover the switch has no power running to the coils from the switch..
I improvised and connected a simple joiner or bridge between the black power - running in to the switch and the black/white from the switch running to the coils.

I now have power when I turn the ignition on to the coils and points (sparks enough to see clearly in daylight when cranking)
and still have everything else operational...progress is good.

I do have a small issue- when I tested the kill switch - my power wire to the kill switch got quite hot and I blew a 15amp fuse. I think this is because I was earthing the power (+) from the battery through the ignition switch to the kill switch then to earth.

I will do a small drawing and try to explain what I have done...

Let me know if I am going in the right direction... thanks

[bryanj]

The kill switch you have is off a later 250/400 twin or CX500 and the two wires are connected to kill the engine SO if you connect the green to the black white what happens is you confyse everyone except you as the kill switch has to be in the off position for the engine to run and dont go when the switch is in the run position. This is because the cdi's are groounded to "Kill" the engine