I'm working on this bike for a friend. It's been ridden regularly, but was brought to me with a specific issue. The bike starts and idles nicely, with a little choke. It revs freely in neutral, sounds fine. When attempting to take off from a dead stop, the revs drop and the bike will stall without clutch and throttle. When it's in this state, a slight application of the choke will 'fix' the issue, but leaves the bike with a high idle. I've been through the carbs twice, they were actually pretty clean in the first place. The owner or a previous owner had attempted the job, as some of the screw heads were cammed a bit. Jets are 110 and 40, the slides drop freely with no friction, the diaphragms look intact, no cracks or holes. Air screws were at 2 1/2 turns out, which I believe is the factory setting. Airbox is stock. Air filter is new, there is no in-line fuel filter. I've removed the jets and the emulsion tubes / nozzles, air screws, everything looked clean, but I used solvent and compressed air on the brass and throttle bodies. I've seen some nasty carbs, but these looked really good, no varnish or corrosion, even the emulsion tubes were clean and untarnished The symptoms improve a bit when the bike warms up, but it's never quite right. Since the problem seems to be across all 4 cylinders, I'm not convinced that I have a carb problem. I'll be trying the starting fluid trick on the intake manifolds, visual appearance of them is pretty good, but I need to try something. My second thought is that I have a fuel delivery issue, perhaps the vacuum actuated petcock. Any advice would be appreciated.