Erratic Speed, misfire, I dunno.

Maybe engine, maybe electrical, maybe both. No idea.

So out of the blue, my 83 kz550 became low on power and kept dying. When I could get it running, It would accelerate very sluggish and want to stall. When I could get higher into the rpm range, it would act as if I was WOT and then chop the throttle closed. This is with me holding the throttle open steady.

I went through the carb today and did a full rebuild. I dont think it needed it, but a couple bowl gaskets were weeping so I did all the work while I had the carb out anyways.

No change in performance or symptoms. Still a bucking bronco

Top end was rebuilt 600 miles ago. No issues, no oil consumption, starts easy cold or hot

Now that fuel has been ruled out, I am leaning towards electrical. ITs a pretty simple system, but before I go diagnosing everything, I wanted to reach out and see if anyone had an issue similar to this.

Any guidance is greatly appreciated!

It may be one of your coils is shot. If you can start your bike you should pull #1 plug. If the bike wants to die then that coil is probably OK. Then try #2 plug. If it starts to die then your coils are OK. If there is no difference then you've found your problem.

Ill look into it! This bike came to me in a box and the plug wires and coils are not OEM or anything I saw on z1. Seems to do this when the motor warms up fully.



Thank again!

Another easy thing to do is to use a spray bomb to spray water on the pipes when the engine is warmed up. If it vaporizes then you know it's firing. If it doesn't vaporize on contact then you have a firing issue with that cylinder.

Just an update for anyone coming along with a similar symptom. I thought about whipping out the multimeter and going through diagnostics, but decided on the old fashioned method of throwing money at it. Based on input here and my previous experience, I opted to replace the ignition coils as its a 10 minute job and used ones are cheap.

In hind sight, I did have the issue sporadically a few months back. It became more and more frequent until this latest fuss where the bike was more or less unridable.

Again, symptoms felt like the bike was being flooded, under powered, failed to idle after warmed up, and if I held the throttle at the same position, it would feel underpowered and then suddenly go wide open for a few seconds and then back to underpower. back and forth... like a bucking bronco

Replaced both ignition coils with a used set off ebay for $30 and she is back to normal! woohoo!

Hooray for cheap and easy!!