1 & 2 cylinders not firing

[Laurence]

hi guys
My 1981 z1000 st will not fire on 1 & 2 cylinders until I rev to 6000 revs any clues would be greatly appreciated
cheers Laurence

[Garry.L]

Welcome.

3 & 4 firing should rule out coils on 1 & 2, so it could be down to leads plugs/caps etc on the electrical side.

Are 1 & 2 getting enough/too much Fuel?. 1 & 2 carb would be fave for collecting crap if the bikes been left for extended periods on the side stand.

Other than the above it's Compression and shim type checks.

[mark d]

Poss check the wires coming from electronic ignition on the right hand side this happened to my st and it was the wire touching on the exhaust pipe after it melted through . This happens on a z rally in 2000 mended it with tape to get home . If it’s not at least you have tested one thing

[z1bman]

if its only 1&2 cylinders it can only be down to fuel

[Mr Bump]

if its only 1&2 cylinders it can only be down to fuel

Yes, most likely. Pull the the choke out when its got some heat in it and see what happens, pull the plugs, check colour, fouling etc plus check for sparks while you're there.

Sounds like the pilot circuits on 1 & 2 carbs are blocked, or possibly fuel starvation from gummed up or stuck float valves.

If the plugs on 3 & 4 are wet or smell of petrol and 1 & 2 are bone dry it's likely the carbs.

Oll

[ogre]

swap the plugs around and rule that out first even if they are new