Z1OwnersClub GB

Hi, I've got a Z1a with standard 28 mm carbs .Lately its been flat off the line,like starved of fuel.The carb internals are original spec and renewed about a year ago.I had the carbs chemically cleaned.It idles ok,but lacks go off the lights.Upjetting will make it run rich.Its got a Harris 4-1 pipe and 115 main jets plus standard idle jets.Any clues?
Thanks Pete

I have a z900 A4 with 150 main jets and it runs fine it also has a harris exhaust fitted and k n filters try some 125 i think 115 are way to small also has 28 mm carbs hope this helps

i used to put 122 jet in with k/n and harris.