Carburetor set-up...Does this look right?

I had a closer look at my bikes carbs and this is the set-up i found. Does this look right?


The vaccuum inlets are set up as such:
Carbs 1 and 4 are tied to each otherin a wish-bone set-up and run under the fuel tank. (Not sure to what)
Carb 2 is tied to the petcock to operate the diaphram in the fuel valve.

Carb 3 was open, which was of my slow idle and strange poppin,. I jury-rigged a cap using a piece of fuel line and slightly bigger cap.

My bike is stalling after a few minutes at highway speed. Capping the no 3 inlet helped, but it didnt solve the problem.

Im not an expert mechanic by any means; much less on motorcycles, but I can only think of two solutions:

1: The fuel diapraghm in the petcock needs BOTH carbs 2 and 3 to operate fully
2: The in-line filter in the main fuel line is visbily kinked (not by me) and is restricting fuel flow.

That's the hookups which my manual shows.

You can rule out the petcock diaphragm by running in PRIME position and seeing if the problem goes away. PRIME is always flowing, whereas ON requires the vacuum.

That's how it set up from new. Make sure that the line from 1-4 going under the Tank is connected and not leaking. It goes to the Fresh Air Vacuum Valve. You can Plug off those Carb nipples as well if you like. Just make sure it's not leaking, as then you will have two carbs with a vacuum leak. Make sure your fuel line has no kinks, and the in-line filter is not restricting flow. You can test that by putting the fuel line into a suitable container, with the filter then without, and turn the petcock to Prime. Keep track of the flow rate, time it. If its restricted, get a filter for a gravity fuel system.

i tried running on PRI after each test ride. It runs a little better; enough to limp home, but doesnt solve the problem.

Check the flow rate, into a container like I said, maybe open the fuel tank cap, in case the vent is blocked. Then there are usually also Screens not just at the Petcock, but in the Carbs, where the Float Needle and Seat are Feed with fuel. They can be blocked. Check the flow from the Tank through your set up. Then move on from there.

@ Motor Head

Ill try that. The fuel filter is kinked on one end (why, i dont know), so Ill check the flow rate like you said.

Thanks

If that line is Kinked replace it. If the fuel filter is the straight type, you want to get a 90 degree one. This will straighten the flow out, as long as it's a Gravity filter. I believe 1/4" is Stock for the Dia, but I use 5/16" through my fuel lines/ filter. It requires some decent clamps though.

All carbs are not the same. What carbs are you using? Ed

650ed wrote: All carbs are not the same. What carbs are you using? Ed

1980 KZ750 H1, Doesn't look to have the Inlet Screens or replaceable Seats on the Float Needles. Keihen CV Carbs.

Shouldn't a couple tubes go from thre carbs to the airbox? Ed

650ed wrote: Shouldn't a couple tubes go from thre carbs to the airbox? Ed

That would be the Bowl Vents. I believe your right he should have TEE fittings between two carbs up high near the rear, with those TEE's having hoses going to the Airbox. That's if it is still stock? Otherwise they would just route down, and hang near the sing arm pivot, along with the drain tubes, and battery vent.
If the bowl vent are plugged off, then fuel won't enter properly, causing starvation.
Good Catch 650ed!
Well the more I look at it I think his bowl vents are through the drain on the bottom. There would be a brass tube inside the bowl reaching above fuel level as a vent, and an overflow circuit. Here the only TEE is 23, and that is the Fuel Tube TEE.

On the 1980 750/4 keihin CV34 carbs wenting is through the overflow tubes. Mine are routed down between the swingarm and the motor. I got a US airbox that had connections and holes for the overflow tubes but I sealed them. There are no bowl screens in the carbs and the seats are not replaceable - pressed in.

I used to use clear line which would harden and kink. I would get about 3 or 4 miles down the road and then splutter splutter. Patton has a good diagram explaining how to get rid of that smog tubing which we never had up here and putting vacuum caps on the 1, 3 and 4 nipples.

The carb nipples in the diagram need to ne either connected to the petcock, connected to the smog tubing which is connected to the valve cover, or capped off.

Good luck - might be worth taking the gas tank off, checking the smog tubing, checking the petocok and putting on some good fuel line with no kinks,