Strange electrics problem

I just acquired a Kawasaki GPX250R (1986, not going), and it has a funny
electrics problem. I'm testing with the battery out of my car, so I
know that's not the cause. All the fuses are OK. When I push the
starter button there is a loud click from the solenoid, nothing else.
Checking with a voltmeter on the starter-motor side of the solenoid, I
see that there is a brief surge of voltage, then it falls back to zero.
One of the three wires connected to the solenoid (apart from the big
connections to the battery and to the starter-motor) shows the same
brief voltage pulse.

If I jumper the battery directly to the start-motor it works fine.
Playing around with the switches I discovered a clue. After the
solenoid click, subsequent starter button pushes do not produce a click
until the on-off switch above the starter button has been turned off and
the button pushed again. To clarify, this is the sequence:

1. Ignition on.
2. On-off switch on (I don't know exactly what this switch is for - the
legend has worn off).
3. Push starter button -> loud click from solenoid.
4. On-off switch off.
5. Push starter button -> faint click from junction box.
6. (Go to 2 and repeat cycle).

I determined that the faint click is coming from the junction box by
putting my ear close to it. The solenoid click will not repeat until
the junction box has clicked. I know, it sounds ridiculous.

The junction box (which holds the 10A fuses) is a sealed unit, so I
can't readily open it up, but I would have thought that it was simply
making connections - no switches.

I presume that the wire I mentioned above (on of the three in the
connector to the solenoid) is the one that activates the solenoid. If I
run a wire from the battery to this connector terminal on the solenoid
the starter-motor fires normally. I conclude that the error is in the
circuit between the starter button and this point. Maybe it is in the
junction box. Parts for this bike are almost impossible to get "off the
shelf" here, and before ordering one from Japan I'd like to be more sure
that it is what I want.

Any ideas?

thanks
Gib

 

Gib Bogle was seen penning the following ode to ... whatever:

That sounds like some kind of protective circuit that's trying to
prevent you from engaging the starter with the engine running. Only,
as you noticed, it ain't working.

That'll be the kill switch. As you noticed, it turns the engine on and
off.

It doesn't - I'd say that the faint click you hear is probably some
kind of safety circuit/circuit breaker resetting itself.

That wouldn't explain the faint click tho'.

Check all the connections - if that doesn't help, you probably have to
open up the junction box to find the bit that goes 'click'.

Might be that the starter is drawing too much current and triggers a
safety circuit before the whole bike goes up in flames...

 

Timo,

Thanks for your thoughts. The starter-motor works OK and turns the
engine over happily with a direct power connection. If I disconnect the
lead to the starter-motor the click sequence I described is unchanged.
Therefore I don't believe that the motor is faulty.

Your comments about a protection relay possibly operating suggest that
too much current might be being drawn somewhere else. Since this occurs
without the starter-motor connected it suggests that there might be a
short in the solenoid activating circuit.

Gib

 

Gib Bogle let forth with a mighty belch and uttered :

Does this bike have sidestand and clutch cut out switches?, if so, eliminate
them.

Does the neutral light work?, if the neutral switch is borked, those
switches may be coming in to play. Does it run when the battery is
connected direct to the starter or just turn over?.

Probably nowt to do with the above, but won't take more than a few minutes
to sort.

 

Timo,

The solution is embarrassingly simple. The "neutral selected" sensor
needs to be connected.

Gib