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1980 GS450, no spark on one side

  • Thread starter Thread starter djg42
  • Start date Start date
D

djg42

Guest
I was riding my bike when all of the sudden it started to rev really high, the throttle was working normally however. I just made it home as the bike died.
When I got home, i realized it was sparking only on one side,
-I checked the resistance on the low tension wires and it was 4.5 on the sparking side and 10.5 on the non-sparking side. both sides were infinite from the low tension wires to the high tension spark plug lead.
Good voltage to both coils,
Do I need 2 new coils, or just one?
How do I check the ignitor?

Thanks for the help!!Its much appreciated,
DJG
 
Last edited:
Dude! Didn't you just replace your igniter? That totally sucks :(

Checking the ignition system is all in your manual. Look there.
 
One way to test your coils and plugs is to unplug your igniter and R/R etc. and manually ground the lead that the igniter grounds. Make doubly sure your igniter etc. is unplugged before doing this though.

Just a quick tap to ground will be enough to see if it sparks or not.

I did this exact thing just last night to confirm if it was my coils or igniter that was bad, and both coils fire the plugs with this test.

It could just be a bad spark plug cap too.
 
Thanks for the great info!
So i unplug the box connector to the ignitor, and then ground the ground wire that would be going into the ignitor to the frame?
Thanks Again,
 
Fristly, I would be ultra paranoid like me and disconnect the ignitor, R/R, stator, and signal generator. I don't want you to risk damaging any of those items by sending spikes through the harness. The igniter has capacitors on the output to suppress the spikes but manually grounding the coil leads isn't nice.

So, once you've done all that, you need to locate the two wires from the igniter connector that go to the coils. On my '82, there's a white one for the left coil and a black with yellow tracer for the right coil (the diagram incorrectly states yellow with black tracer, but it's the reverse).

According to the Clymer yours should be the same, but best to be sure. The wire you don't want grounded is the one with 12 volts to it, which should be yellow with white.

Once you've identified the two, then yes, just sort of flick them to ground rapidly to see if you get a spark on both sides.

If there is no spark on one side still, then you need to do resistance checks again.

If there's infinite resistance from the primary to the spark plug cap, give the spark plug cap a screw in and try again.

If that still fails, unscrew the spark plug cap off the end of the HT lead and measure from the primary to the HT lead. If that's still infinite, sounds like the coil is buggered.

If that measures ok, get yourself a pair of NGK XB05F spark plug caps and replace them both at the same time. They're a cheap fix compared to new coils if you don't need them.

With all of the above, you can swap the order and do the resistance checks first, there's no specific reason to do either first, except that making a spark like that is kinda fun :)
 
thanks pete!
What do you think about the intermittent high revving?
i mean HIGH, like full throttle. The throttle seemed ot be operating normally though, and the intake boots looked good,
 
Either your throttle is sticking or you have an intake leak somewhere - more likely the latter. What's the condition of your petcock vacuum line? have you replaced the intake boot o-rings? Are the sync taps tightly sealed?
 
When mine was together and running, if I left it with the choke on for too long when warming it up it would do that.

However, I'm more inclined to agree with Mike with regards to intake stuff...
 
thanks guys! The intake boots are good, but im gong to check the sync taps+vacuum line,
 
Thansk for all the help!
It turns out, both the ignitor and left side coil were bad. My (+) battery terminal had become so worn and finally just snapped off, never noticed.
This is the second time my ignitor blew, both times were after I lost the battery power, why does that fry these things?

As far as the intermittent high reving, still haven't figured it out, its only happened once recently, and Ive rode around alot. It doesnt seem to be the throttle cable, or intake boots, i put in new o-orings.
 
I'm very close to a cheap ignitor alternative... stay tuned to my ignitor thread below.
 
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