Z1OwnersClub GB

Hello guys/ladies, I'm a new member and need a wee bit of helpful advice, etc
I have a KZ900 A4 (2 years) I love it, but it is not running 100%. The issue is it splutters at low speeds and not the kind of power I would have expected from a 900.
Each pot compression checks ok, bucket shims adjusted, carbs sonically cleaned and set, new coils, leads, caps, new electronic ignition, a new rectifier/regulator on the way, dropped down to B7ES plugs, which are black once taken out (Running rich) removed the air filter for a couple of miles and the splutter was gone but no power, Electrical or Carbs issues? I am not sure and I am losing faith after all the above changes and would like to hear from an expert in the Z1 owners club if you don't mind. Needles and jets are possible reasons, what are the standard sizes of jets etc for the Mikuni 26mm KZ900 carbs?

Welcome, one possible cause is weak spark. Have you checked the voltage at the coils? The kill switch and 40+ plus yo wiring loom and connectors are possible causes for low voltage at the coils causing a weak spark and black plugs.

choke plunger seals ?

I would have said choke plunger seals as well, if only to eliminate them from the possible faults!

Check fuel level in carbs, i.e. float height and float needle valve sealing, get decent ones, a lot of rubbish out there, happened to me.