97 GSX lost spark

[97gts717]

Hello everyone. I have put about 2.5 hours on my new to me 97 gsx and it has been great, until today.

About 30 minutes into my ride today, I was cruising about half throttle and all of the sudden it died as if I pulled the key. It would crank but wouldn’t restart and I figured it had lost spark. Anyways, got towed back to the dock and when I got home I checked compression which was a perfect 155-155. Determined that I lost spark on both cylinders.

My question is, where do I start? I’m not as much familiar with these 787’s as the 717s so I could use some guidance of exactly where and what to do. Thanks.

 

[Ckrawiec]

So, you've verified that there is no spark at the plug end by taking off the spark boot, removing the spark plug, putting the plug back into the boot and laying the spark plug so the tip is against the engine then hitting the start button? You should (or not) see a spark jumping the gap on the end of the plug.

Of course it could happen, but losing spark like that might not be the problem. When was the last carb service if you know? Losing fuel delivery is a far more likely scenario than losing spark....but it could happen.

 

[97gts717]

So, you've verified that there is no spark at the plug end by taking off the spark boot, removing the spark plug, putting the plug back into the boot and laying the spark plug so the tip is against the engine then hitting the start button? You should (or not) see a spark jumping the gap on the end of the plug.

Of course it could happen, but losing spark like that might not be the problem. When was the last carb service if you know? Losing fuel delivery is a far more likely scenario than losing spark....but it could happen.

There is no spark. I have verified that there is no spark on either cylinder.

 

[Ckrawiec]

OK then....no spark situation.......have you trimmed 1/4" off the ends of the spark wires into the boots and retried that for spark? Then check all the ignition coil grounds, wiring, etc.....then replace the ignition coil if everything else is ruled out.

Start with the cheap and easy stuff first.....good luck!

 

[POPPS]

If this is a 785,,,with rear electrical box,,,remove the box,,,remove the white connector going to the coil,,,put a test light in the white connector, and of course the test cable to ground,,,hit the start button,,,if the light pulses,,your problem is at the coil or the ground tower ,,,if it does not pulse,,,then your problem is up stream from the electrical box, ,

 

[97gts717]

If this is a 785,,,with rear electrical box,,,remove the box,,,remove the white connector going to the coil,,,put a test light in the white connector, and of course the test cable to ground,,,hit the start button,,,if the light pulses,,your problem is at the coil or the ground tower ,,,if it does not pulse,,,then your problem is up stream from the electrical box, ,

I did test this with a multimeter and got .6v while cranking

 

[POPPS]

I don't use a multimeter, nor do I know how much the voltage output is,,,I use a test light and watch it "pulse",,,it would appear that you have a signal pulse to the coil,,,and that the issue would be in the electrical box.,,ground,,,or coil,,,

 

[Jtamaro]

A lot of good stuff already mentioned, just check each and every fuse. Make sure you physically pull them out and check for corrosion too

 

[97gts717]

I don't use a multimeter, nor do I know how much the voltage output is,,,I use a test light and watch it "pulse",,,it would appear that you have a signal pulse to the coil,,,and that the issue would be in the electrical box.,,ground,,,or coil,,,

With a multimeter on DC volt mode between the white wire on coil and ground. Initially it read 0v and when I cranked the engine over it held 7v while cranking. Where do I go from here ?

 

[artr]

As Popps said you appear to have a signal into the coil. There is probably a spec of the input and output resistance of the coil and how to measure it it in the service manual. Popps also mentioned grounds. There is a long screw/bolt in the rear electrical Box that has a lot of ground connections on it that tend to get corroded over time. Take it apart and clean up the connections.

 

[97gts717]

As Popps said you appear to have a signal into the coil. There is probably a spec of the input and output resistance of the coil and how to measure it it in the service manual. Popps also mentioned grounds. There is a long screw/bolt in the rear electrical Box that has a lot of ground connections on it that tend to get corroded over time. Take it apart and clean up the connections.

Already done that. It’s either the stator or the MPEM that is cooked. Going to rip into stator and check it out

 

[POPPS]

The stator will not be responsible for the no spark pulse,,,but the pickup/trigger will,,,and then down stream to the cdi/rev limiter,,of course ,,,please help me here,,,put a test light in series with the white connector to the coil and battery ground,,,and see if it pulses,,,then we can definitely zero-in on your problem.

 

[97gts717]

The stator will not be responsible for the no spark pulse,,,but the pickup/trigger will,,,and then down stream to the cdi/rev limiter,,of course ,,,please help me here,,,put a test light in series with the white connector to the coil and battery ground,,,and see if it pulses,,,then we can definitely zero-in on your problem.

Found the issue. The trigger coil indeed broke off and was hanging in the Mag housing. Thanks for the advice

 

[POPPS]

Way to go...a "happy ending!"