No fuel out of carbs

Hey folks, my apologies if I missed a thread on it but I took a look and couldn't find my exact problem, I have a project 83 GPZ 750 I picked up recently and have gotten everything but the carbs working. No matter what I do cleaning wise I cannot get any fuel to actually make it from the bowl out of the pilot circuit. The bike will fire right up on spray. I have the rack apart again for a second time but can't seem to find the issue

What I've done so far
Cleaned all jets and slides
Sprayed brake clean through the pilot in the bowl and seen it come out the top
Sprayed brake clean through both holes on the inlet side and seen it come out of the main and dribble out of the pilot
Checked that all floats are balanced and will fill the bowl but not overflow
Checked bowl vent tubes for blockages (gas will pour freely if I turn them upside down while full

My vacuum on carb two is not connected to the tank because that's its own issue, I have been feeding it with external fuel but I have some caps showing up tomorrow to cap it. Carb 3 was already capped and 1/4 are connected with the factory T going to the valve cover

Currently lost as to what to do with this guy. I also checked that it is not the model with the plugs and connector from main to pilot, it's the straight pilot carb

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If you haven't already i recommend you get a service manual to solve any preliminary issues. 

First off, I cant quite understand what you're saying about the vacuum lines. You're putting fuel in through the vacuum nipple??? The nipple in the bottom of the middle of the carb rack is the fuel supply (should be 8mm or 5/16). For vacuum I would make sure that all of the vacuum nipples are either capped off or connected to something so there isnt open vacuum. for now if you can, just block it with your finger when trying to start it to see what happens.

You're almost there but I would do a full carb service to isolate the issue. That would be making sure that everything moves smoothly, no o-rings are cracked or brittle, service the float level, carb passages are clean, etc. Be careful using brake parts cleaner around those o-rings!

It also looks like there is supposed to be a plug above the pilot jet so make sure that you have those and o-rings that seal otherwise it'll run very poorly. Edit: my mistake.

Good luck and pictures would be greatly appreciated!

bound wrote:

If you haven't already i recommend you get a service manual to solve any preliminary issues. 

First off, I cant quite understand what you're saying about the vacuum lines. You're putting fuel in through the vacuum nipple??? The nipple in the bottom of the middle of the carb rack is the fuel supply (should be 8mm or 5/16). For vacuum I would make sure that all of the vacuum nipples are either capped off or connected to something so there isnt open vacuum. for now if you can, just block it with your finger when trying to start it to see what happens.

You're almost there but I would do a full carb service to isolate the issue. That would be making sure that everything moves smoothly, no o-rings are cracked or brittle, service the float level, carb passages are clean, etc. Be careful using brake parts cleaner around those o-rings!

It also looks like there is supposed to be a plug above the pilot jet so make sure that you have those and o-rings that seal otherwise it'll run very poorly. Edit: my mistake.

Good luck and pictures would be greatly appreciated!


 

As in the factory vacuum line from carb 2 to the petcock was not connected. I fixed this today by capping all 4 carb ports and deleting the VSV as per some other threads but still the same issue.


Let me know what pictures would be useful, I have the rack back on the table again after a few more failed attempts at getting fuel to pass through either circuit. I'm assuming this is an issue with air getting into whatever passageway it needs to but the ones I can find I can spray through with brake clean no issue

Check fuel level in carb bowls with clear tube on the bowl drain.?

Floats upside down ?

when you state that cleaner sprayed into the pilot comes "out the top", where is that? is there anywhere in the bowl area that you can spray, that the spray comes out on the intake side of the carb throat? what about the fuel adjustment screw at the top of the carb? is it fully closed? are your throttle plates fully closed?

Spraying up through the pilot jet will have it come out the pilot outlet above the throttle valve, same goes for the inlet at the intake. If I spray the other one it comes out the main jet into the bowl
Butterflies are all closed unless I turn in the idle speed adjustment screw 

I have been following this topic but have not responded as of yet as I was not sure I could provide any useful suggestions. You indicate that no matter what you do no gas is getting pulled up from the bowl into the pilot circuit when you attempt to start it. Have you checked to makes sure there is fuel in the bowls, if you have and stated so I missed it. But if no fuel in the bowl nothing but air will get pulled up. If you have not the next time you put it together and try to start it, after allowing fuel to get to the bowls, open a bowl drain screw. (you will want some small container to catch any fuel coming out) and see. If there is none or very little then it would appear the issue is in the fuel not getting to the carbs.

 

All 4 bowls fill with no issue. Some reason or another it's not pulling it out of there, hoping there's an o ring or passageway I'm unaware of somewhere that could cause it to lose vacuum

Just spent some more time looking at the carbs also, it appears the rubber boots on the carb haven't aged the best. It's a bit late to try it tonight but tomorrow I'm thinking I try spraying on those while cranking the bike, I'm assuming these boots exist to create an air seal for the choke tube and that this could be my problem. If it is, do these parts even exist anymore or would I have to get something else to try to replace it?

OK thanks for the additional info. I can not say if new cab holders (that between the carbs and the head) will make a difference. But come on the stock ones would be rather old.Will say that spraying something at them is not the best way to find leaks. That is unless they are leaking bad.

The dust seals on the carb itself for the choke, not the boots on the head. Somewhere there has to be enough of an air leak to not want to draw any fuel

Cracked or perished choke plunger dust seals won't have any significant affect on starting.