DT400 wont start- ignition problem?

Hi there,

New to the forums and already have a question!

Me and some mates are building up a 1976 dt400 that was sitting in another mates yard for many years. The motor had put the rod through the crankcase, so we purchased a replacement motor. The replacement motor is out of a 1975 MX400.

We wired up the new motor with basic wiring (no lights, etc)- but cant seem to get it started. We used the CDI and the coil of the original DT400 motor.

However, we seem to be having a bit of an electrical problem.

When we try to kick it over there is no spark. But when we disconnect the earth on the CDI and kick it over for a bit, and then connect the earth again we get a spark (as soon as its re-earthed).

Do we have a faulty pulser coil, CDI unit, or coil? Or even something else?

If any electrically minded people could shed some light on our situation it would greatly appreciated!


Do you have the full ignition from the MX400 engine?  I am suspecting that there is a wiring problem that happened when you swapped CDI and coil from the DT400 to the MX400.

Those old bikes were very, very similar in the engine departments, however there are several differences when you start looking into the wiring looms and the external ignition bits and pieces.


I would try the full MX400 ignition first to see if the bike fires up, that way you know you have a runner.  Then I would worry about getting the rest of the DT400 chassis wired to the MX400 engine.

We do not unfortunately. I am contacting the guy we bougth it off to see if he still has the wiring.


It also turns out the motor is out of a DT400c (1975)- I would have assumed the CDI and Coil can be used, but it seems not as there is a stray cord coming of the stator plate (green and white) which needs to be connected to the CDI. Problem is, our CDI has no where to connect it.

It might not help you, I have a friend's Cr250 here and the guys selling it to him did not have a OEM CDI so they installed a chinese bike's cdi which burned after a few hours so it seems.


I have a RM250 full electrical system here and I'm about to install the entire Rm250 Electrics onto the CR250, so far it looks as if it would fit. Sure the little PV electrical Unit will have no usage but it did neither have one with the Chinese Bike's CDI. 


I think you could buy a complete system of another bike and make it work.

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