New 79 cb750k owner with ???'s

[Bludgeon]

Hey guys,
 New here and new to bike maintenance in general so forgive or flame me as you see fit!

 Anyhoo...79 cb750k, 4600 miles, starts but runs like a 3 legged horse and sputters and dies without choking it. Pulled the plugs, soaking wet and half fouled. SO...

What I have done so far...
-New plugs gapped correctly
-Cleared cylinders
-Disassembled, soaked and cleaned, rebuilt carbs
-Checked tank for trash
-Checked fuel filter
-Checked air filter


Here's the kicker...

The bike was running but running BADLY when this began, but as soon as I took off the carbs, the plugs now get ZERO fire. Tested all 4 outside the cylinders for arcing and not a one is getting spark now.

Thoughts? Suggestions? Tomatoes thrown at the new guy?

Coils? Wires?

To my knowledge the wires and coils are factory as was most everything on this otherwise mint lil ride.


Thanks in advance
-Bludgeon

[blackhawkrider]

Is the kill switch in the on position. I know that sounds stupid so most likely it is. Its odd none of the plugs spark. When you did this test did you ground the plug to the frame somehow. Its not your coils there is more than one and if one was bad some plugs would still spark. Very unlikely that both would go out at the same time. I am not sure if you bike has points or ignition module but that could be it too. I would start with the easy stuff first though fuses, wires, and connection point before ripping much off

[Bludgeon]

Hey thanks for the reply.

Yup switch was on, and the strange thing is...this same test was fine on 3 of the four cylinders just the other day. Ignition is module in 79 up I think of course I could be wrong, but could it be that module just shorted out suddenly? all the fuses are good. Kind of frustrating, to be honest.

Thanks
-Bludgeon

[blackhawkrider]

electrical problems are frustrating but usually once you find the problem quick and easy to fix. I looked up your bike it has two ignition modules as well as two coils. Again start with the easy stuff make sure your wires are connected well on both ends coil and plug and that they are going to the right spots. Next in your manual it should give you specs for where the coils resistance should be check those first. Then if the check out I would move on to ignition modules. It is rare these blow unless there was a major surge or someone messes them up. since the icms cost so much I would also verify with a dealer or someone else who can test them for you so you don't waste money buying a part you think is the problem but isn't. Its worth the $40 so you don't waste $300. I have learned that the hard way and still occasionally do it. Don't know why. Let me know what happens.