KZ750 four blows main fuse.

Hi all! New to the forum, and hope you folks can help me with this;

Got this '82 Kawasaki KZ750E about two weeks ago. Trucked it home and found the main fuse blown, and it continues to blow each one I put in, killing all the rest of the electricals. Does this after the engine starts to get warm, and I've yet to ride it because of this. With the key on but the engine not running, the fuse lasts.

I have traced all the wiring, neck bundles, headlight grommet area, etc....everything, and found only a few frays that I repaired. Didn't help. One thing I did find was a wire (white with red stripe) coming off the starter relay end of the positive battery cable. When I measured for continuity from the wire to ground, I got at least 200 ohms (key off, battery out, all switches off). The wire goes to the regulator. There shouldn't be any continuity here, or there will be a voltage leak from the battery when the bike is parked. How is the regulator tested?

Could this be related to the blowing fuses? Also, where is the regulator? Can't find it...or, is it under the battery box, and if so, how do I get it out?

im guessing something in charging system reg/rec ? look under side cover or under battery box

Could test charging system by measuring battery voltage across battery terminals at idle rpm and again at 3000~4000 rpm.

Look for 13+ volts at idle and 14~15 volts at 3000~4000 rpm.

Excessive charging voltage (say over 16) may indicate regulator failure or an issue with its associated wiring or connectors.

Insufficient charging voltage could indicate rectifier (or possibly alternator failure) or defects in associated wiring or connectors.

My KZ900 is fitted with a combination reg-rec unit from Z1E that's located under the battery box and accessible from underneath the bike. Am guessing location would be the same on '82KZ750E.

Good Luck!

I'd try that test if I could keep it running long enough, but it usually fries the fuse within a few seconds of starting now.

With the key on but the engine not running, the fuse lasts.

When fuse remains intact with ignition switch ON, but fuse blows with engine running --- am suspecting a charging system issue because those components (alternator, rectifier, regulator and associated wiring and connectors) function only with engine running.

Overcharging is usually not from an alternator or rectifier malfunction, and this leaves the regulator (and its associated wiring) as prime suspect. Would double-check for any frayed wiring insulation, and also integrity of the wiring connections.

The FSM likely includes more specific regulator testing procedures, both in circuit and out of circuit.

But with a 27 year old non-serviceable sealed electrical part suspected of malfunctioning (and its wiring looks okay), I prefer just replacing it with a new component, thinking if it isn't already defective, it might be tomorrow, likely somewhere out in the boonies :pinch:. And besides, it's easy for me to spend your money. :lol:

Here are links to the combo units available from Z1E.

With Connector

Without Connector

Good Luck!

No, the SM (the one I have anyway) speaks about doing resistance tests between the three yellow wires and the wht/red wire (and then also the black wire) and then simply states "...there will be 10 times more resistance in one direction then the other." Which isn't nearly as helpful as actual numbers would be.

Interesting website, but at those prices the bike can stay in the garage. Surely someone must offer this part at a better price. I remember that the last one I bought (for a Honda) was about $27!

polkat wrote:

No, the SM (the one I have anyway) speaks about doing resistance tests between the three yellow wires and the wht/red wire (and then also the black wire) and then simply states "...there will be 10 times more resistance in one direction then the other." Which isn't nearly as helpful as actual numbers would be.

Interesting website, but at those prices the bike can stay in the garage. Surely someone must offer this part at a better price. I remember that the last one I bought (for a Honda) was about $27!

three yellow wires--- probably referring to the alternator, which produces alternating current (imo not a likely fuse blowing suspect).

10 times more resistance in one direction then the other--- probably referring to the rectifier, which converts the a.c. into d.c. (imo not a likely fuse blowing suspect).

Imo the official Kawasaki Motorcycle Service Manual for a particular model is far superior to any of the aftermarket service manuals. The official KHI manuals often appear on ebay.

Remember to check integrity of the wiring and connectors associated with the exiting regulator. And look for frayed insulation maybe causing a short in the wire bundle routed between the reg/rec and connectors.

Good Luck!

Yes, it's a test for the regulator/rectifier. I did find something odd though. The regulator passes voltage from the battery to ground when all switches are off (bike parked)!! It comes down the battery + cable to the starter, where it passes on through a wht/red wire (voltage sensor wire?) to the regulator, then out the black wire of the regulator to ground. The resistance from the black wire (disconnected) to ground is about 200ohms and the voltage drop across this is about 3 volts. No wonder the battery won't stay charged.

Now, I know that this just ain't right! Could it also be causing the main fuse short?

If needed, this link will provide a button whereby an on-site wiring diagram may be downloaded.

Click here to show download button

Good Luck!

Not needed, but thanks! Trying to figure out why the regulator is shorting.

polkat wrote:

Hi all! New to the forum, and hope you folks can help me with this;

Got this '82 Kawasaki KZ750E about two weeks ago. Trucked it home and found the main fuse blown, and it continues to blow each one I put in, killing all the rest of the electricals. Does this after the engine starts to get warm, and I've yet to ride it because of this. With the key on but the engine not running, the fuse lasts.

[snip]

Could this be related to the blowing fuses? Also, where is the regulator? Can't find it...or, is it under the battery box, and if so, how do I get it out?

If the fuse will last when the engine is off, but will pop when its running, the most likely culprit is your charging system.

Do the stator tests with the engine off (you'll need to unplug it from the main harness) If it tests as good (and it probably will) try running the engine with the stator unplugged and see if the fuse lives and you get the ~60 Volts AC from the stator leads.

There are tests on reg/rect (yours should be a combined unit) that you can do with it off of the bike. (they're in the service manual and you'll want one for this) If it fails these then you'll need to replace it (there's nothing user serviceable inside) before you plunk down $100 for a new one, check the rest of your battery connections etc. bad connections can cause resistance and other faults.

It wouldn't hurt to have the battery load tested either to make it'll hold a charge for you.

hope this helps... Sam

polkat wrote:

Hi all! New to the forum, and hope you folks can help me with this;

Got this '82 Kawasaki KZ750E about two weeks ago. Trucked it home and found the main fuse blown, and it continues to blow each one I put in, killing all the rest of the electricals. Does this after the engine starts to get warm, and I've yet to ride it because of this. With the key on but the engine not running, the fuse lasts.



Could this be related to the blowing fuses? Also, where is the regulator? Can't find it...or, is it under the battery box, and if so, how do I get it out?

I'm having a near identical problem with my 1982 KZ750 E3, however my main fuse will last while the bike is idling (at least for now), and blows when I start off in first gear. This happened for the first time when I was pulling away from a stop light. Replaced the main fuse, started the bike, let it idle to warm up, started out in first gear and....BAM! Blows main fuse again.

I attempted the reg/rectifier test w/ an ohm meter as stated in the service manual, but cannot seem to measure any resistance as stated in the procedure. In addition, the connectors from the reg/rect to the starter relay and the connector from the + battery terminal to the main fuse are blackened and have melted the plastic covering a bit.

I'll attempt the voltage measurement at idle and RPMs as indicated in Clymer manual, however I'm thinking the the regulator is malfunctioning and instead of sending excess voltage to ground, it is sending it straight to the main fuse, causing the blown fuse situation.