breaking up

Hi Guys,

A 76 KZ750 Twin. Pods, rejetted, good runner for 2 summers until recent.

Rode to work last week, fine on the way there, about 20 miles.

The 1st mile home after starting fine, breaking up at about 3000 RPM. Not just less power, breaking down feeling. Sometimes I could push through the breaking up by giving more throttle.

Figured I would start with fresh plugs, took it out today with same results. Checked plugs after 1/2 mile ride and they are black.

all electrics appear to be original including coil and wires. Timing/ gap in spec. Breaker points discolored on one side of contacts but not pitted. Battery is at 10 v and same at coil. I have the charger on it now, and should get 12 v but expect same results. Could weak battery cause this kind of behavior? It starts easily with kicker, elec starter never spins motor for me, I think because of battery.

Have a little one to take care of so thought I would reach out to you folks to maximize the limited garage time.

Thank You!

Yes low voltage to ignition could definately cause rough running.
How old is battery,Have you checked the output of charging system with bike running?
At idle Id expect minimum of 12v and it should increase to around 14v as you rev it up a little

I will check voltage tomorrow while running. Way to loud to check now. I put it on trickle charger an hour ago and is now reading 12 v. I suspect though if I hopped on now, I would get same results. i do not know how old battery is. Am I correct in thinking I have an electrical problem due to new plugs getting black so quickly? I am assuming the only change in fuel supply at this point would be a lean condition from clogged passages/jets and plugs do not seem to suggest this.

Carbon fouled plugs would be symptom of low voltage (DC)...

It doesn't sound like much but a 2 volt drop off is a significant loss of voltage/current to the plugs.

As mentioned, measure your idle and 4K running dc voltages insuring your charging system (Vac->VDC Rectifier/Regulator) is to specifications. Possibly a poor ground in the charging circuit where power leaving the battery but not fully returning.

Is battery sealed/AGM/Gel or lead acid...?
If lead acid... dump it and go AGM!

Ah hell, since you don't know how old the battery is, dump it and start fresh otherwise you may be chasing this all over the place or worse stranded due to a crap battery.

Not sure which B series you have so just in case you need....

OK...here we go. Turns out I did not have an elec problem after all. Those of you familier w/ Mikuni BS38; the Needle Plate worked loose on one of the carbs, allowing the needle to raise and come out of needle jet. When I bought this bike and initially tore it down, the other carb had the same problem, however the needle didn't come completely out of jet. Anybody see this? Maybe I should start a new thread.

Hi This is a Kawasaki KZ750 LTD H 2 -81. Crankshaft axial clearance wonder if