I thought you'd said nothing much happened when you removed the cut-off valve? If it stalls, that not so bad. It does show it's running on the idle circuit as does the sucking noise. I see many busses where exssentially someone's just given up and set the idle speed with the throttle stops, then someone else down the line has adjusted everything and the whole thing is to pot. Anyway... It should keep running, but at about 450 revs. If it won't run without wire, I'd suggest you wind the mixture screws out a bit, wire back, start, warm up, remove wire and then see. As you need to have it running like this to set the mixtures I find it's best to start with them too far out so it's more likely to run, then adjust them (Like you I do give it a go with all screws out 3 turns first). I would imagine when you then reconnect the wire the revs will be too high. Turn them down with the big screw, then set the mixture screw on top of the carb and a final adjust of the speed. Works for me.
Yes not much happens (revs do drop a bit)when i remove the central idling valve(the biggest cutoff valve) the problem is when i remove the smaller cutoff valve wire. When i remove the wire from the valve on the right carb the revs drop about 400rpm, but when i remove the wire from the left carb the engine just cuts out.
I well out of my depth in this thread as ive never worked with twin carbs before However since we no longer have the karma option with a little message on the late bay i have to do things open like this Id like to say well done and what a cracking dude zed is for helping you through this I know what im on about with loads of vehicle related stuff but when zed pipes up with advice hes rarely wrong and id always follow his advice
There are 3 cut-off solenoids. 2 are just that - cut off fuel to each carb, pull the wire and it'll run on two cylinders or stop. The other is the central idling sytem cut-off. Pull this one and it should run on the carbs "driving" idle jets at about 450rpm as stated above. If "not much happens" when the central idle wire is removed, I'd suggest your throttle stops (or one of them) are screwed in too far allowing to much air air through the main body of the carb, which drags fuel through the idle jets and runs without much help from the central idling system. I would suspect it's the one that stops the engine when you pull it's cut-off wire off as it must be running on this one? People get confused here because the most common method of setting idle speed is with the throttle stops as most don't have a central idling system. Once someone has mistakenly taken this approach it's start again time.
The amount of single carbs I've tuned that have had the throttle stop wound open as opposed to the idle circuit adjusted... it's mad!! lol
Perhaps people who'd previously tinkered with old Beetles? Ours only had a mixture screw and it was correct to set the idle with the throttle stop. And a vac only distributor.
There's usually been some sort of method in the madness I think. Or should that be the other way round?
The throttle stops are set correctly, i have even removed the carbs again to double check this, i also tried winding the throttle stop screws right out and that didn't make any difference. The only thing i can think of is that the idle jet on the right carb could be blocked? as the problem is when i remove the left carb cutoff, so its telling me the right carb idle isn't working?
All sorted now when i took out the cutoff solenoid and looked closely at the end of it, it looked a bit out of shape(may have been dropped) which must have been restricting the fuel flow at idle.
