No spark. Help!

[NC81cafe]

Alrighty so this is my first bike and I'm learning the ins and outs. I've always been a wrencher on cars but never a bike. I got my 81 gs450s as a trade non running. Harness has been pretty modified by the PO unfortunately. I do know him tho and the bike did run. No ignition or gauges, completely naked. Basic relay put in for starter.

So here is the issue. I've got no spark. I've got power going to the coils. And thru the wires to the plugs. The bike will turn over normally but just won't spark.

The bike has a new battery (full charge)
Replaced the ignitor from one off eBay from a running bike.
Has an aftermarket R/R
Brand new dc3-1 dyna coils.

I'm not so good electrically, definitely a more mechanically minded person, but what could be causing no spark if I've got power going to the plugs. The mechanical advance? Is there a way to test that?

Potentially looking looking at building a complete new harness from a spare harness that came with the bike. If y'all think that would be the best route for a naked bike with minimum electrics, is there a harness diagram I could follow?

Thanks for all your help in advance!

[almarconi]

Even if the coils have power if they are not receiving a signal from ignitor they will not spark. You have a signal generator on the end of the crank that is connected to the ignitor. When the ignitor gets a signal from the signal generator it tells the coil(s) to fire. It could be something simple like bad plugs or a broken wire. Do you have a wiring diagram? There is a procedure to test the ignitor in the service manual, I can't remember how to do it off the top of my head. Trace the wires from the ignitor to the coils ( should be orange/white, yellow/black and white).

[NC81cafe]

Thanks for the reply. I do have two ignitors for the bike now so I will test them. But everything to the coils is good. I'll take the covering off to check for bad connections/wiring. The plugs are brand new so won't be those. Either I have another bad ignitor or my signal generator is bad? How can I test that?

[almarconi]

Here is the procedure to test the ignitor

Remove each spark plug of #3 and #4 cylinders, fit it
to the plug caps and place it on the cylinder head.

Remove the frame cover on the right side and disconnect the lead
wire from the signal generator.

Connect + lead of voltmeter (set on ohms) with blue lead
wire on the ignitor side and - lead on the voltmeter with the green
lead wire.
The moment the test pins are connected the spark plug of #4 sparks
and the moment the tester pins are disconnected the spark plug of
#3 cylinder sparks.

To test the pickup:

If the pickup still is mounted to the bike, disconnect the wires and add an LED between them (any LED from anything will work). Turn the engine over.....if the led lights the pickup is working. If its off the bike, add the led and just wave a magnet over the pickup.....if it lights it works.

[NC81cafe]

Don't think it matters but it's a 450 twin... so just cylinders 1 and 2.

[almarconi]

The above procedure was from a 750 shop manual but I don't think it will make much difference. The 4 cylinder bikes have a 1-4 signal and a 2-3 signal from the ignitor.