It runs. Sort of.........

[Chris Cochran]

Well, I had some rare time to work on the Voyager again and I got the carbs back in and everything hooked up. I tried starting it and it RUNS!
For all of 15 to 20 seconds before it conks out.
I've had it running perhaps a dozen times but never for more than that length of time before crapping out.
There is fuel in the bowls, so the gas pump seems to be off the hook.
Quite honestly, I fed up with this thing.

[GrandpaDenny]

Couple of things off the top of my head:
1. Is the choke set properly?
2. Did you try adjusting the idle speed screw?
3. Check the bottom of the fuel tank the metal line from the tank could be smushed by the swingarm.

[triton28]

Chris;
since you mentioned the engine does in fact run, albeit for only 15 seconds, one would think that fuel in the carb bowls is NOT the problem. The next bit you are not going to want to hear because while you are saying there is fuel in the float bowls the symptom is reminiscent of a lack of fuel in the float bowls.
This, should my theory be correct of course, would indicate to me one or more of several possibilities.
If your bike IS a California model then loosen the gas cap a bit to see if the gas tank is under a vacuum when the gas cap is tightened shut. Not a desirable condition.
If your bike is NOT a California model then make sure the overflow hoses for the gas tank are not blocked or pinched. The tank has to be able to vent to allow for fuel flow to the filter/pump.
Eugene Kapuscinski once posted about persons who use a worm gear clamp on the hose/nipple connection of the fuel hose to the pump located at the bottom of the gas tank. The swingarm gas tank hose connection area is VERY limited in it's clearance to the swingarm and with this type of clamp there is the possibility that when the rear wheel is under compression and the swing arm travels upward the nipple, now having limited clearance when this type of clamp is used with the screwdriver worm gear on the downside, bends as a result of contact with the swingarm. Sometimes the amount of bend is enough to restrict the flow of gas to the pump thereby providing less than the required amount of gas for any given amount of time. This situation is often overlooked so have a quick look at yours and either include it as a possibility or eliminate it.
Provided the 2 aforementioned conditions are OK then the flow to the filter/pump needs to be verified for quantity. Carefully and gently clamp the hose to the filter from the tank shut and then disconnect the hose from the fuel filter inlet side. Now, being prepared with a suitable catch basin for the gas which IS going to flow from the hose and the disconnected filter inlet nipple, release your homemade hose clamping device and check for full flow of fuel to the filter inlet nipple from the gas tank. If the flow of gas seems unobstructed and free flowing then reconnect the hose to the "Known Clean Filter", or install a new filter. Repeat for the hose to the pump from the filter and if this hose is clear and free flowing then one can assume that fuel delivery to the pump is present and adequate.
REMEMBER; during all this hose checking one will need a method of ensuring the unchecked flow from the gas tank is being controlled and not bleeding out all over your floor through an open ended hose.
Next, having reconnected the hoses from the tank to the filter and from the filter to the pump and removing any clamping shutoff device one has used to control the unchecked flow of fuel, one will need to disconnect the hose from the fuel pump to the carburetor fuel inlet tee and direct the open end to a suitable catch container. Now operate the fuel pump and check for the full free flow of gasoline from the open hose end. Note that the volume of gas will not be a "Gusher" of fuel but should be a steady soft flow at around 2-3 lbs. of pressure. As well one can stop the pump by providing a resistance to the hose until the cut off pressure of 2-3 lbs of the pump is achieved at which time the pump will stop pumping. Let the resistance go and the pump should start pumping again. If you do not get this soft regular flow of gas then either the pump is faulty or the fuel hose from the pump to the carburetor fuel inlet tee is blocked/kinked.
So now that you have discovered and/or eliminated any fuel delivery problem one would assume that all would be well. Unfortunately there are several possibilities still left to check and the one that comes to mind most are the float needle valve hangers. Carl Leo has oft posted about the aftermarket hangers NOT working as do the OEM needle valve hangers. Generally this problem is the opposite of yours in that the condition is one of flooding of fuel out of the bowl overflows. I am sure though that these hangers could just as easily malfunction shut.
However if you have the original hangers AND the float levels are set at the manual specification of 17mm then perhaps you may have plugged internal pilot sequence passages inside the body of the carb/s thus restricting the amount of fuel available for the engine to run properly ONCE the fuel level in the float bowls is consumed and lowering. This requires a soak overnight in a putrid smelling but effective carb cleaning solution such as Berrymans or Kleen-flo 651 Carburetor and Metal Parts Cleaner and then an ultrasonic bath to get the varnish/crud out of these internal passages.
I hope I am wrong in your case but this diatribe is what I would go through should I be experiencing your symptoms.
Don't get too frustrated as these old bikes are well worth the learning curve to get them working properly.
I hope this may be of some thought provoking assistance,
regards
Dave

[Nails]

... and the one that comes to mind most are the float needle valve hangers. Carl Leo has oft posted about the aftermarket hangers NOT working as do the OEM needle valve hangers.

The floats swing with very little clearance. I've seen them bind on sealant applied to the float bowl gasket ... graphically illustrating why gasket sealer isn't supposed to be used there.