1982 KZ750 LTD - blowing main 20A fuse

Long time reader....first time forum composer.

Need some help here people....

Just completed a top end rebuild of a 1982 kz750 ltd; rings/cylinder hone/gaskets/etc. Prior to re-installing the ignition coils and gas tank, ignition key, when turned, would turn on front headlight.

After coil/gas tank re-install, turn ignition key and (you guessed it)....NOTHING!

Installed new battery....still nothing.

Checked fuse panel under left side cover and (ahhh haaa) main 20A fuse is blown. Picked up some 20A replacement fuses....turn the ignition key and main 20A fuse replacement fuse burns up immediately.

Any suggestions? Hoping I am a "simple" (if there is such a thing) electrical solution away from hearing this baby fire up!

With the exception of this electrical issue at the end of the project, I cannot believe how easy this top end tear apart and rebuild has been.

Thanks for any help that can be provided.

Check the ignition coils and how they are mounted. Dyna and Accel primary wires(the smaller ones) come really close to the bolts. Check for pinched wires too.

Also here's a testing procedure:

The Dreaded Shorting/Intermittent Electrical Problem!


Here is the most basic method I know(Taken from www.kzrider.com by member Patton)

1. Charge your battery and have it load tested if you can. The floating ball hydrometer can be used to check the specific gravity of the charged cells in the battery.

2. Disconnect the Black lead from the (-) Battery terminal... or Red from the (+) Battery terminal, it does not matter which one. Just 1, not both!

3. Connect one of the following test setups in series with the Battery terminal and lead:
3.1 A 12 V light bulb,
3.2 A 12 V test light,
3.3 A 12 V test buzzer or,
3.4 A 12 V horn... you get the idea.

4. With the Ignition Switch OFF, go through your harness and wiggle the wires while looking/listening for the test setup to go on/start buzzing.

5.With the Ignition Switch ON, repeat the test except this time the looking/listening for the test setup to go off/stop buzzing.

6. Be prepared to open the Ignition switch and check/test for solder joint failure and or circuit board micro breaks (don't ask how I know this).

7. Be prepared to pull the wires out of the Head Light to test for failures at or near the grommet.

8. Be prepared to open the harness at or near the Steering Neck for failures. This is where wires tend to exhibit fatigue due to repetitive movement.

9. Be prepared to open the left and right switch gear to search for rust and or broken parts. CAUTION: watch out for flying springs, ball bearings and stuff. Do indoors on White sheet (again don't ask ).

10. Be prepared to follow the heavy gauge wire from the Starter Solenoid (Relay) to the starter for bare wire exposure. Especially near bends and grommets.

11. If you can reproduce the fault symptom your are pretty much home free. Be prepare to find and repair/replace any internal wire breaks, insulation break downs, exposed wires, rubber grommet failures, etc. Often, shrink tubing will solve the problem temporarily until something better can be done.

12. I use a very good electrical contact cleaner/preservative called De-oxit made by Caig Labs in San Diego Ca. Their website is www.deoxit.com It can be purchased at Radio Shack and any other electronic supply store. I use it on all of my motorcycle’s electrical connectors , in my home entertainment center’s stereo patch cords and cordless phones charging cradles.

Tough break on the short. Had one on my 400 that took 2 weeks to track down. If you don't have it, download the color wiring diagram from the filebase and check everything connected to the 20 amp circuit for continuity. Since you obviously pulled the tank, the part of the loom that runs under it is first priority.

Good luck!

P.S. I'd just go ahead and buy lots of 20 amp fuses now.....you'll go through'em in the testing.

thanks MFolks and Link14....

This was some extremely helpful insight!

If there is no followup post over the next week or two weeks...well...it wont be hard to guess what I will be doing in my garage!

Gotta love the electrical systems on these bikes, huh?

Solution discovered....

I, unknowingly, when reinstalling the throttle body had pinched a wire in the starter.

Luckily, I discovered this prior to spending tons of time troubleshooting through the remainder of the electrical system.

Have a great spark on the plugs, however, I am having some difficulty getting it started.

One issue corrected and another presents itself....welcome to owning a 1980s kawasaki!