Poor fuel delivery

[danish6259]

Hey everyone. Just finished my latest re-re-rebuild on my cb500 Four and have come into a small problem.
For some reason the fuel isn't flowing out of the tank and into the carbs at a steady pace. I constantly have air bubbles in the lines and the won't go away. The carbs have been completely rebuilt, ultrasonic cleaned and the fuel tank is clean and re-lined with a free flowing petcock. The bike runs and even with the vacuum of the intake, it doesn't flow in any better. Any thoughts as to what could be causing this? Thanks in advance.

 

[axeugene27]

i would think the only reason for this would be clogged vents in carbs that is if you have good flow when they aren't hooked up to the carbs. Is your gas cap vent clean?

 

[teddpage]

This is kinda a stab in the dark, but if you open the fuel cap does it flow any better? The fuel cap has a vent to allow the fuel to flow freely. Think about when you pour a drink and it comes out "glug glug glug", now add a vent, smooth pouring. Make sense?

 

[danish6259]

Having the tank cap open doesn't do anything for flow rate. I've even given the tank a small positive air pressure and it didn't help. I have a feeling it might be something internally with the cabs but I want to try and eliminate everything else before I split them open again.

 

[axeugene27]

yeah like does the fuel flow well when they are not hooked up to the carbs?????

 

[danish6259]

Just pulled the tank off to double check and it flows like a champ even with the cap closed.

 

[Swapmeet Louie]

check you bowls for casting slag, the floats could be hanging up on them. If so, file them smooth.

 

[danish6259]

That definitely isn't a problem. I glass bead blasted the entire carbs so they are as clean new. I'm tearing into them right now and will check all the porting and see if anything might be clogging them but so far everything looks to be clear.

 

[danish6259]

Well, whatever was causing the problem is now gone. Blew out all the ports with some compressed air and the fuel lines. Reassembled everything and hooked it all back up, turned the fuel on and it flew down into the carbs and not a single bubble came back up. Started right up on the second kick too.

 

[teddpage]

Glad you got it all cleared up! Now go ride that sumbitch!