1980 gs1000 weak/no spark

[revilo]

Hi folks.

I've got a 1980 GS1000G. Trying to get it started this spring and encountering problems. The bike will occasionally start but will usually die quickly. Sometimes it is only running on one or two cylinders. I've checked for spark with a plug on the head and sometimes will get spark, sometimes not. The sparks that are occasionally produced have been very weak. This doesnt change with a fully charged battery. The carbs were thoroughly cleaned over the winter and are clearly delivering fuel to the cylinders (I can see and smell the fuel on the plugs)so I dont think that is the problem. The bike ran fine when I put it away last fall but wouldn't start over the winter when I would try to turn it over.

So, I am assuming coil or igniter issues. I found coil testing tutorials but not bike specific and im not sure what ohm values to expect from the Suzuki units. Can anyone help? I'd also like to know how to test the igniter, and pointers on any other possibilities would be gratefully received.

Thanks in advance!

 

[Redman]

Coils are quite reliable. But can check ohms of primary and secondary, per specs in book.
Ignitors can fail, but when do get no spark at all.

Other things to check: VOltage at the coils, the Org/wht wire. SHould be pretty much same as battery voltage. But sometimes can have problems at fuse block, and ignition swtich and connecotrs that lower the voltage before it gets to the coil. Tell us what you find.

Other things to check: Spark plug caps. Assuming the orignal type (resistive) caps, used with original type wires (non-resitive), the caps should be 5k ohms. They can fail over time and heat. They can be pulled-twisted off the wires. DOnt need to be stock caps,most places carry the NGK brand. Check the ohms. We can talk more if find a couple that are bad (higher ohms than 5K). Also look at the end of the strands in the wires.

 

[salty_monk]

A lot of times there is dirt in the connectors leading to low voltage at the coils. Very common. Sometimes even after cleaning all the connectors it's still not great. The answer is to run a switched relay to deliver full volts to the coils. Lots of info about that here.

The Dyna S is a very easy modification on that bike too if the ignitor box has gone. Mine did.... Not a no spark fail a "it runs fine till 5,500 - 6,000 rpm fail" when it just fell over.

I would also run it in the dark and look for sparks. Often the plug wires crack and spark "escapes" to the fins on the head... You can replace them but occasionally you can't get them out of the coil & need to replace the coil too...

These are all issues I had with that exact same model bike...

 

[Grimly]

An often overlooked connection is where the lead from the igntion pickups attach to the loom and/or ignitor box. The slightest corrosion there drops the very small signal voltage enough to make it problematical.

I can feel it in mine - it's still running fine, but a slightly harsh tendency of vibration creeps in. Usually cured by cleaning all ignitor connections.