Righty ho . This is my first post. I have 2 400's both gk73's i think . Ones a rolling chassis and the other was a working bike and I was using it . Its always ran a bit crap cutting out occasionally and being a bugger to start . But now it will start on choke but the moment you take it off choke it dies. I checked jets and idle screw is 1.3/4 turns out. I have tried the carbs on the other bike and still the same . Any ideas . I'm thinking o rings .

If the o,rings are worn it will run rich so should smoke and the temp gaug stays low.
73's are prone to airbox leaks that cause weak running.