Re: gsxr 750 starting problem

randy pape wrote:
> my friend says no spark now and he thinks some battery fluid might have
> leaked into the coil area . i'll have to go there and see what he's talking
> about. thanks for the replies. i do think this is an electrical problem
> though.

Well, the ignition coils would be right up over the valve cover and
battery acid just could NOT get there, because the battery is lower,
it's under the rider's ***. Battery acid might have gotten onto the
ignition module though. Check out the connectors, etc. for corrosion
and acid damage...

You can easily check the ignition coils by disconnecting the plugs from
the ignition module and hook 12 volts DC from the battery to the + side
of the coil
and momentarily touching a lead from the minus side to ground, while
watching the spark plugs, which you've removed and grounded to the
frame...

You might consider taking the ignition module (or the whole motorbike)
to a $uzuki $tealer$hip in hopes that they still have a ignition module
tester after
15 years. Ya never know...

You may find what I'm about to tell you confusing. I'll admit that I'm
uncertain about what you've got with the ignitor box, that's why $uzuki
can charge you so much money for a new one...

Even if you had a 1988 GSXR-750 manual, the wiring diagram wouldn't
show you the circuitry inside the ignition box, you gotta be a
electronics *wizard* to dig that thang. I bet Bob Prohaska would
understand this. Google him up and ping him to see what he knows...

The ignitor unit on the early model carbureted GSXR's *just* has two
large power transistors (or silicon control rectifiers) inside it and
some ignition retarding circuitry that counts the pulses from the
signal generator coil on the right hand side of the engine.

Counting pulses also drives the rev limiter and the tachometer

The power transistors are just solid state replacements for the old
ignition points that we used to have to clean and reset all the time...

That all sounds so simple, like the answer is *just* a thought away,
but it isn't so simple...

There are two plugs on the 1988 ignitor box, one plug has four or five
wires and probably is the power input/ouput wiring for the coils and a
ground wire. The other plug is probably the signal input from the
signal generator, I can't tell by looking at the signal generator parts
fiche...

Anyway, what happens is when you turn the key on, the coils get power
and the circuit to ground is completed through the two transistors in
the ignitor box...

When one of the steel teeth on the ignition rotor on the right hand
side of the engine passes the signal generator coil/magnet assembly, a
very small voltage of maybe 2 volts is generated momentarily because
the magnetic field is disturbed. That voltage goes up the wiring from
the signal generator to the appropriate power transistor in the igniton
box and it momentarily causes that transistor to stop conducting
electricity...

(I don't *think* that the signal generator coil ever gets any voltage
FROM the ignitor box, I think it only sends a small voltage TO the
ignitor box.)

When the 12 volts from the battery stops going through the ignition
coil, the electromagnetic field in the coil primary collapses and
induces a higher voltage in the secondary winding. This causes a spark
on the #1 and #4 sparkplugs or on the #2 and #3 plugs, depending on
which tooth passed the signal generator coil...

Since the power transistors are conducting electicity from the ignition
coils to ground, if you take out all the spark plugs and put them back
in their lead caps and ground them to the cylinder head, you should see
a spark at the gap of at least two spark plugs whenever you turn the
ignition key on. I'm not sure with this ignition box, but you might see
a spark at the OTHER pair of spark plugs when you turn the key off.
That test would at least tell you if the transistors in the ignition
box are conducting electricity...

The 1988 GSXR-750 apparently only has ONE signal generator coil and a
two-toothed rotor that does double duty, compared to the 1986 GSXR-750
that has two signal generator coils and a one-toothed rotor...

Either way, two cylinders are going to get a spark every 180 degrees of
crankshaft rotation...

It seems like the DC trigger pulse coming from the lone signal
generator coil would have to be the SAME POLARITY every time it pulsed.
You can probably figure out which wire is positive and which wire is
negative when the pulse comes through it by hooking up an analog
voltmeter set on a very low voltage scale, the pulse is going to be
like about 2 or 3 volts...

It's critical to know the right polarity for the pulse if you're going
to try what I'm going to describe. You're totally on your own, you can
blow out the transistors in the expen$ive ignitor box if you apply
voltage of the wrong polarity to the signal generator input pins on the
ignitor box. If the signal generator coil is pulsing out a low voltage
signal every time one of the rotor's teeth passes it while you crank
the engine over with the starter, you know that the signal generator is
working...

See, there's a *1.5 volt battery test* you might try to test the
ignition box. Again, you're totally on your own doing the 1.5 volt
battery test described below and you blow up the ignitor unit...

My 1986 GSXR-750 has TWO signal generator coils instead of one, and the
official shop manual tells me that I need Suzuki's special ignition box
tester to check the box. It says to remove two spark plugs from
adjacent cylinders, reconnect the caps and ground the plugs to the
cylinder head and flip the switch on the box with the igniton switch
turned on. So far as I can tell, there's nothing in that box except a
1.5 volt battery and some switches....

My 1982 GS-1100EZ also has TWO signal generator coils. But they are
connected in *series* unlike the 1986 GSXR-750's signal generator
coils, which don't appear to be connected together at all...

The Clymer manual says that I can take the spark plugs for
the GS-1100's #3 and #4 cylinders out, reconnect the high tension leads
and lay the plugs on the cylinder head. Then I can disconnect the blue
and green wires from the ignitor unit and apply 1.5 volts DC from the
positive side of a flashlight battery to the blue wire. When I connect
the negative side to the green wire the #4 plug should fire. When I
disconnect the negative wire from the green wire, the #3 plug should
fire...

I suppose one power transistor in the GS-1100EZ's ignitor box is an
NPN, the other is a PNP. All that NPN and PNP business means is that
there are either two layers of negatively doped silicon with a thin
layer of positively doped silicon, like a sandwich making up the
transistor, or there are two layers of positively doped silicon with a
thin negative layer in the sandwich center...

To switch the transistor OFF and fire the spark plug, the NPN
transistor needs
a small positive voltage applied to it, and to switch the PNP
transistor off the transistor needs a small negative voltage to the
center of the sandwich...

And the two signal generator coils hooked up in series on the GS1100
provide a positive pulse one time and a negative pulse the next time...

At least that's what I remember from studying transistors 25 years
ago...

That would explain the Clymer manual's caution about hooking up the 1.5
volt battery with the correct polarity, positive to the blue wire,
negative to the green wire...

But this business about the 1988 GSXR-750 having only ONE pulser coil
leads me to wonder if it doesn't *always* put out a positive signal
from from one of the signal generator leads and a negative signal from
the other and if the transistors inside the ignitor box aren't both
NPN's or PNP's?

The shop manual for my GSXR-750 with the two signal generator coils
claims that the signal generator coils are alternately turning the two
transistors ON and OFF. I think the manual may be wrong though, from
what I understand BOTH the transistors should be ON anytime the
ignition key is on. I would expect both ignition coils to have power to
the + terminals when the key is ON and that would disprove what the
manual says, to my way of thinking...

The Clymer manual also says that the correct resistance for the
GS-1100EZ signal generator is 250 to 360 ohms...

A GS1100G owner said that *his* signal generator coil showed 160 ohms
through the coil...

My GSXR-750 shop manual says that the signal generator resistance
should be 130 to 180 ohms. The ignition coil's primary resistance
should be 3 to 5 ohms, and the secondary resistance from one plug cap
to the other plug cap should be 25,000 to 45,000 ohms...

.

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