78 650 dropping 2 cylinders

While riding, 2 cylinders will randomly stop firing. Sometimes I can ride it out and they will just randomly kick back in... other times I'll have to shut down and restart, but even then it doesn't always start on all 4. I'm running pods and a 4-1 exhaust. Any ideas as to the cause? Does it sound more like a carb issue, or electrical?

Thanks for your any recommendations!

Can you tell which 2 cylinders quit? Cylinders 1 & 4 are fired from one coil; 2 & 3 are fired from the other. Each coil is triggered by its own set of points. So if you have one set of points, one coil, or the wiring between them fail you will lose two cylinders. Since it is intermittent, I would start by checking and cleaning the connectors for the circuits from the points to the coils, if it still happens check the coils and no matter what if the points and condensers haven't been replaced in recent memory go ahead and replace them. Ed

brademan76 wrote: While riding, 2 cylinders will randomly stop firing. Sometimes I can ride it out and they will just randomly kick back in... other times I'll have to shut down and restart, but even then it doesn't always start on all 4. I'm running pods and a 4-1 exhaust. Any ideas as to the cause? Does it sound more like a carb issue, or electrical? Thanks for your any recommendations!

Could be an issue with spark quality (for whatever reason), or compression (valve clearances), or fuel mixture, or any combination of these.

To begin diagnosis --

Would perform the clear tube test on each carb;

Would remove the plugs and examine spark quality, looking for fat blue sparks;

Would assure valve clearances being within specs.

Good Fortune!

Thank you gentlemen. I will try some of these electrical diagnosis in the next day or two and report back!

Check the sparkplug caps, on bike with stock ignition wiring, the caps will unscrew from the sparkplug wires. Then take a multimeter, and check the 5000 ohm resistor inside, as they will cook with time and become unreliable. When replacing the caps, cut about 1/4" off the end for a clean connection.

Finally had some time to get into the bike yesterday. I should also add that the bike has a dynatek 2000 ignition system.

I swapped the coils and was still only firing on 1-4, so that tells me its not the coils. I pulled out plug 3 and fired the bike up and wasn't getting a spark at all. Could the dynatek unit itself be going bad or maybe its the wiring from the ignition system to the coil. I suppose I can check that with an ohmeter.

Thanks for the help.

Thanks to another member for helping point out this thread... Breezy was having the EXACT same issues... sounds like a bad module so its time to Annie up $300 for another one unless Dyanatek will work out a deal with me...

www.kzrider.com/forum/2-engine/463907-kz...from-dyna-s-ignition