I'm cunfuzed

I have a 1977 kz650 which loses all power randomly an comes back randomly

Bad connections or fuel restriction?
Steve

Willy1803 wrote: I have a 1977 kz650 which loses all power randomly an comes back randomly

If not electrical....
Possibly fuel starvation from tank to carbs,
Fuel bowls run low, engine craps out, engine requires very little fuel to limp on and then bowls get a chance to refill a bit.

Check for kinks in the fuel line.

Check battery cable connections at both ends.

Is the battery good or old? A bad battery in a 1977 KZ650 can cause symptoms similar to those you describe. Ed

Remove the Tank, Headlight, and sit down and unplug and re plug every connection you can find, checking for melting or corrosion at the same time..

By loose all power I mean electrical power all the light's go out

Willy1803 wrote: By loose all power I mean electrical power all the light's go out

Check the fuse holders for corrosion or looseness... Etc.

Can someone tell me what this is an why it is smoking

It might be a hazard regulator. Unplug it and see what happens.
Steve

That is the bike's rectifier, and it should NOT smoke. It converts the A/C current produced by the bike's alternator into D/C current used by the bike's electrical system. It contains diodes that can fail. The Kawasaki Service Manual contains simple instructions on how to test the unit. Later bikes have the rectifier and voltage regulator together in a combination unit, but the 1977 KZ650 models came with separate units. If yours has failed it can be easily replaced by one from www.oregonmotorcycleparts.com/Products.html . I replaced mine several years ago when it failed. Pictures of the original unit that came on my 1977 KZ650 are sown below. Ed