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I recently received a 78 honda cb400 as a project. I thought it would be no problem to get it running, I was wrong. It has no spark. I got the coil checked and it was fine. I was told to unplug the ignition switch behind the headlight, after doing this it fired. I put starting fluid down the cylinders and it started long enough to run out the fluid. I repeated the starting fluid again and now once again no spark. any ideas.

First thing is to find the electrical problem and fix that. Spark that comes and goes is a sign that something is grounding out or a connection is breaking someplace, and intermittently. So it's going to suck finding it. Best to get a schematic and a voltmeter and start at the battery. Check your entire system from the ignition switch to the starter button circuit, to the engine ignition (piontsand wires etc...) and everything inbetween, lights, etc.

And then it sounds like you need to clean the carbs well to get fuel to the engine.