Heat Soak?

David Fallon davidinwa at comcast.net
Tue Feb 3 12:21:40 PST 2009

Thanks; the coil swapping is a good idea.  I'll check for temperature  
too.  Electronic alright.  That means the pick up coils could be doing  
the heat soak too.

David Fallon

Charles wrote:
Hi David,

I owned a sweet 81 KZ750 and I will agree it's a blast to
ride, I miss it a lot.

What you are describing sounds like an overheated ignition
coil.  It gets hot while riding and when you park it it the
rising engine heat is too much for it and it overheats.
Once you drive it for a few miles, the cool air lowers the
temp enough that the coil kicks back in and it runs fine.

Question 1 is is yours an electronic ignition, I am
assuming it is.  If not, I'd check the point gap as too
wide of points will overheat a coil.  If it is electronic
ignition, you might try some shielding to that coil or swap
the two coils and see if the 2&3 drop out while the 1&4 now
run.  I'm thinking that somewhere it is a heat problem with
that one coil.

Charles S.

> Hi;
> I'm hoping someone's experience will save me some
> trouble.  The last three times I have ridden my 80 KZ750
> it has gone down to two cylinders when restarted.  I have
> ridden for about an hour getting to my destination.  About
> an hour later I come back to the bike to ride
> home.  When I start the engine, it runs on only two
> cylinders; the #2-3 combo.  The #1-4 are dead with no
> spark as they share the ignition.  I have enough power
> with two cylinders so I head for home.
> After about 3 miles, the dead ignition kicks in with no
> further trouble.  It runs great all the way home.
> I cleaned the wire connectors, tightened the connectors,
> ohmed out the  sensors and box which all test good per the
> manual.  A few months ago, I installed new Dyna coils.
> When I installed the coils, I worked all the 12V
> connections to the coils to reduce the voltage loss in
> that long convoluted wiring mess.
> I'm wondering, is this the classic heat soak behavior of
> the solid state device?  Is swapping on other components
> the only way to check?
> Thanks  for any advice or pointers.
> The KZ is too much fun for an old guy like me!
> David Fallon

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