No ignition, no spark


XS400 New Member
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Hello everyone,

I know there are numerous post concerning the motorcycle not starting due to having no spark. My DOHC 1983 XS400 is having the same problem, the absence of a spark at both spark plugs. The motorcycle had problems suddenly shutting down from time to time. But now, after a thorough cleaning, it doesn't give us any spark at all.

Now, I've been reading posts for the last two weeks, but still no solution was found. A listing of all I've done you can see below:

-Reassured the battery was full (12,5V). I even used a car battery to be able to draw more power to the starting motor.
-Checked the spark by holding the spark plugs against the engine block.
-Checked the fuses and connections.
-Checked groundings
-Measured resistace of ignition coils: primary (2,5 ohm) secondary (8 ohm)
-Measured resistance of pickup coil: 112 ohm

So far the troubleshooting as written in the manual at page 6-22 and 6-23 which you can find on this forum.

Then I noticed thad only 9,57 V was entering the TCI unit instead of the 12V supply from the battery. Consequently most of the connections were checked.
-At that moment the battery had 12,06V.
-At the main fuse the 11,40V arrived.
-Then the circuit goes to the key contact and subsequently to the ingition fuse were 10,51V was measured.
-After the emergency stop contact, we had 9,99V left.
-At the TCI 9,57V was read.

I tought that maybe the 9,57V supply at the TCI was the problem. The connections were cleaned and even an external 12V supply was connected tot it. Using an oscilloscope, the outputs to the ignition coils was read out as noise. This suggest that the TCI could be faulty. When opening the TCI box, I saw a minimum of corrosion. It might be possible that somehow a drop of water entered the box after 38 years.

To conlude this post. There is no spark, I've run out of options and I'm affraid that I need to buy an aftermarket TCI. Can someone please help?


Good evening,

Me and my dad changed the TCI with one he found on the internet. Fortunately there were clear sparks at the plugs. Now, I'm looking to fix the original TCI. Hopefully it is a bad soldering or a malfunctioning transistor.


Solder and transistors are the common failure points in the old TCI boxes. Both are cheap fixes if you are good with a soldering iron.