Smoke from under the seat. ribbed unit hot

I was riding tonight and came in to my friends house and at stop the engine died, then smoke from under the seat, The ribbed electrical unit was smoking and hot, Battery went dead,Help please 1976 KZ900A

I presume that ribbed unit is this one?



That's your regulator-rectifier, the device that converts the three-phase AC voltage from your alternator to ~14V to run your electronics and charge your battery. If you have a generator instead of an alternator, much the same function - it will lower the voltage to about 14V (but no rectification required for a generator).

Luckily when they die they usually just cut out and stop charging. They can get hot in normal use (that's why they're ribbed), but certainly shouldn't smoke. If you're unlucky, it's let too much voltage though, but I've never seen this happen (but I've never dealt with generators,which I think your bike may have).

If it's smoking you'll need another anyway, so get a new one. If it had failed, it won't charge your battery - this might be what stopped the bike. Hopefully it hasn't damaged anything else - I've never seen it happen, but it could. Charge your battery, change out the regulator/rectifier, and start it up again. Get a voltmeter and check the output from the regulator/rectifier. It should be about 14V when the bike is running. Might be a bit lower at low revs, especially if you have lights on.

If you're game to start it up again with the old one still in place, charge the battery, and hook a multimeter across the battery terminals before starting it up. When it starts, check the voltage - shouldn't get any higher than about 14.5V. Hold it at higher revs, and it should do the same thing. If the voltage is no higher than the voltage before you started the bike, it's not working. If it's higher than 14.5V, it's over-charging. Don't keep it running if the voltage is too high. If it's too low, not an issue, it will just drain your battery.

No offense intended, but it sounds like it's time for you to buy a Kawasaki Service Manual for your bike. Assuming you plan to keep the bike you need to at the very least be able to identify the bike's various components. Your description of a "ribbed electrical unit" implies you have some brushing up to do. If you get the manual and read through it you will be amazed at how easy it is to understand the different systems on the bike; it is a great resource. They usually are available on eBay; just be sure to get one for your bike's exact year & model as there are differences. No one has ever regretted buying one. Ed

The 76 KZ 900 has a alternator. Unless it's been converted, it has a separate regulator and rectifier. The rectifier on these get very hot. The early regulators had a bad habit of overcharging the battery when they go bad. Pics?
Steve

Oregon Motorcycle Parts might have a rectifier. or maybe a combo unit that can be retrofitted. ???

It's easy to do.
Steve

650ed wrote: . . . buy a Kawasaki Service Manual . . . to understand the different systems on the bike . . . No one has ever regretted buying one. . . .

Here's a reference pic from Ed's old BSA manual :lol:




Good Fortune!

:woohoo:
Now that's funny.
Steve

This page may show a blank, but the information is there, about rectifier fires on the older Kawasaki 4's

www.redlinecycle.com/rectifiers.html

Patton wrote:

650ed wrote: . . . buy a Kawasaki Service Manual . . . to understand the different systems on the bike . . . No one has ever regretted buying one. . . .

Here's a reference pic from Ed's old BSA manual :lol:

Good Fortune!

:laugh: :laugh: :laugh: :laugh: True! In fact, I sold the BSA because the Genuine Lucas Wiring Harness Smoke was not longer available from the dealer. Without that smoke I never new if the Lucas electrics was working or not.

My rectifier desoldered two of the diodes. I took one out of a 650 Yamaha twin. I ran that until I parked it. Two years ago I bought a combo unit used. I'm now on my second one. Used stock KZ 1000's. Next time it will be one like shown. End of problem.
Steve

Op get a multimeter and browse the forum for regulators and charging , don't fit a new component until you have diagnosed the problem otherwise that could go up in smoke too $$$.