TOPIC:

Hi, I just refurbished my Z400 and got it running. Everything worked like a charm and i ran through inspection with zero remarks, then took a tour of some miles. Then i left the bike in the garage for a week, then I changed the handlebar. Then when i went for a ride, it fired right up and was left to warm for a minute, then i sat up and it ran like a bag of nuts! Weak, coughing, slow response and then died. Then it was hard to start and would not run for more than a couple of seconds. I recharged the battery and tried the next day, same results.
The spark looked a bit weak, so i proded arount on the contacts and the spark got better. Then i tried to start again (fully charged battery) and it would not start at all, running on the starter and coughing a bit now and then. I rechecked the sparks and now they sparked just occasionally!

Wat can be wrong? What ohms should the coil have? How do I check the ignition system? My bike has a contactless system (its from 1982).

OH just to mention! I put the old handlebar back to be sure, if it was some ground through the handlebar or something. No difference...

Go to the home page of this website and download the service manual. It is down the page a bit, on the right. The link starts out .... kz400500550.....
The service manual will have troubleshooting tips as well as test specifications for the electrical components. It sounds like you may have a bad coil, but there are other possibilities.

I followed the manual and built a ignition testing rig to make the coil produce a spark between two nails 7mm apart when i pushed a button. At first it worked fine and so the pickup was to blame. but after a while it started to miss most of my puches on the button. It just sparked now and then. A pattern I recognize.
But this does not give me clear results, not reliable...

Is it possible to use some universal aftermarket CDI and/or coil? The original ones are always old and expensive!

These things are known for excessive voltage drop in the ignition circuit.

Take a voltmeter and check voltage from post to post on the battery. Then take the positive lead of the voltmeter and connect it to the "hot" wire on the coil (ignition on). The difference between the two readings is the voltage drop between the battery and the coil. If it's more than .5volt, run a jumper wire from battery positive to the "hot" wire at the coil. Then start it, and see if that fixed the problem.

This is a good quick check before going any further.

Aight! Nice tip, but no dice. There where no considerable difference in voltage...

Have you compared spark while cranking from the two coils separately. If one is good, the other bad, that narrows things down.

A bad coil or pickup will only kill one. Bad ignition module or insufficient power and/or ground to the module or coils will typically kill both.

It seems very coincidental with the handlebar swap. That's what I would suspect. You probably had to do a lot of moving of the harness. Every bike I've rewired always had many defects (from wear) in the harness where the frame harness goes to the steering area (usually into the headlight bucket).

If the bike is from 82, then it probably has one or more interlock circuits in addition to the power and control wires for the ignition.

As a temporary test, I would hardwire a power wire from the ignitor to the battery and also a ground wire. This hardwire would also power the coils.

Sometimes the 12 volts at the coil can be deceptive. Tests good static but a poor connection fails under load when the coil is pulsed with a ground from the module. A jumper from B+ to the hot side of the coil would be more conclusive. I think it should apply more direct voltage to the module from there also. But you can go direct to the "ignition on" terminal at the module to be sure. Of course, poor ground circuit to the module will produce similar symptoms.

I think on my bike the circuit went: fuse box > ignition switch > kill switch > coils/module

Again, are you losing spark at 1 or both coils?

How long did you let it sit there and idle?

Hi, I think something is wrong with the ignintion system on my Z400-R1 1982.
I can find brand new ignition coils on ebay for z400 up to 1979. But from 1981 all bikes has a transistorized ignition system. Does this mean that there is some difference between the coils?

I think I will by a new CDI also, but they are more expencive and always pre-owned

VTEC wrote: Have you compared spark while cranking from the two coils separately. If one is good, the other bad, that narrows things down.

A bad coil or pickup will only kill one. Bad ignition module or insufficient power and/or ground to the module or coils will typically kill both.

The Z400 uses a wasted spark system and has only one coil that sparks on every turn of the crank, this makes it harder...

Okay so it seems like the next thing to try is to power the ignition system directly from the battery. should i remove the existing connection through the kill switch and that or will that give me problems?

Baldy110: I don't know, maybe a couple of minutes... but now i can't even get it started at all. The problem seems to get worse and worse for every time I try. (that is wierd)