Splitting fuel line

[rybeatty]

Ok I've got a question for you guys about splitting fuel lines. I replaced my stock tank with a sporty tank which obviously only has one petcock so Ive had to split the line using a brass T just above the carbs. The problem I am having is when the float bowls are empty and I turn the gas on the fuel is flowing until the bowls are full then it cuts off usually with with carb having more fuel in the line than the other than when I start the bike the one with the less fuel empties causing the bike to die because it's not getting fuel fast enough to keep it full. There is no line obstructions, the cap is vented and the tank is brand new so I know there is nothing getting in the line. I'm really not trying to spend a bill on a duel outlet petcock.

 

[gggGary]

If the tee isn't blocked I suspect something stuck in the inlet of that carb that dies, almost completely blocking fuel flow. These bikes will run fine on one normal size petcock. The factory changed to just one in 1980.

 

[rybeatty]

They are brand new vm34's. There's no blockage because when I take the nut off the bottom of the bowl gas flows out.

 

[Brew]

have you tried bleeding/pinching the line to get the excess air out?

 

[Brassneck]

There's no way to connect the two bowls (Like in the BS38's) right?

Since they are gravity fed, the best fix is to ensure that the line is full of fuel all the time (When on) so that one carb can't go dry...maybe creating a lower "chamber" with lines so there is always gas that they draw from (perhaps a three pronged fuel filter exists?)

Or, I'm wondering if perhaps routing the initial fuel line to a more central spot (Like over the the center rail on the frame and then down (so that the flow of fuel is less towards one side than the other)?

 

[RFeng]

They are brand new vm34's. There's no blockage because when I take the nut off the bottom of the bowl gas flows out.

No wait - all that tells you is your bowls have fuel. Clean the carbs again.

 

[gggGary]

I kinda recall that when I had "madness" going (two petcocks, VM carbs) that I would "pump" the air out of the fuel lines each time I had drained the float bowls. I had see through tygon lines, turn on the petcock and squeeze a fuel line a few times, it forces the air out of the line into the tank. Once the air is out it should stay out. The float valves act as check valves.

 

[Brew]

i'm betting that one line is longer than the other and when the shorter one gets full it blocks that T-spliter up.

 

[Brew]

I have 34's that each have their own line to the tank with in-line fuel valves and have to pinch both to get the air out all the time. After a few pinches and the air is out no problemo.

 

[rybeatty]

Thanks for the input guys. Yeah one line is longer than the other. I'm gonna change it up so they are both the same length and try the pinching idea to force the air out and bring fuel down.

 

[gggGary]

Just a heads up that fuel line routing is very fussy about gravity flow minimum loops bends all downhill to the carbs. But really if the float valve opens, gas will normally flow alongside and bypass any air bubbles. How old are the VM34s? IIRC older designs have the main jet fairly high the newer ones have it way down in the sump to reduce low fuel starvation problems.

 

[rybeatty]

They are new carbs and they have the real low main jet