Fuel Line Too Short?

[GPz1100]

I took off the tank for the first time and noticed there was no slack in the fuel line. When I went to put everything back together I had a very hard time getting the fuel line on. Apparently I pulled it loose on the other end because it didn't take long and I had gas running down the front of the engine.

I figure it's not supposed to be that tight and at some point in the bikes life it's been cut. So...is the fuel line normally that tight?

[signart]

There really is no slack for a reason. You might want to use a worm gear clamp.

[salty1]

A pretty tight fit, some slack, not much. As you say, a PO MAY have messed with it.

[YoungPUP]

Be careful if you decide to replace it. There is a very fine line between too long  and perfect.  If it goes too long it sag and will starve the motor of fuel.  (Or so I've been told  )

[ecw]

I'm going to claim that any concerns about lengthening the fuel line are a myth.  Physics says that as long as the carburetors remain the same distance below the fuel tank, you will get the same flow.  I suppose that if you made the fuel line 100 feet long you could notice less flow.  If the hose goes above the fuel tank, then there might be some conditions when you could "vapor lock" the hose at the high point...

I haven't had any problems with lengthening the fuel line in my limited experience, but perhaps someone has actually seen an issue?

[Valkpilot]

I'm going to claim that any concerns about lengthening the fuel line are a myth.  Physics says that as long as the carburetors remain the same distance below the fuel tank, you will get the same flow.  I suppose that if you made the fuel line 100 feet long you could notice less flow.  If the hose goes above the fuel tank, then there might be some conditions when you could "vapor lock" the hose at the high point...

I haven't had any problems with lengthening the fuel line in my limited experience, but perhaps someone has actually seen an issue?

There are lots of cases recounted on the tech board of folks adding extra fuel line then having problems with fuel starvation and the appearance of being out of gas while the tank still had a gallon or two in it.  Shortening the fuel line usually cures the problem (unless the petcock or vent function is also involved.)

If you pull the tank and look at the way the fuel tine runs, there's not a lot of drop in the first part of teh line.  It is basically level from the petcock to where it splits to feed the two fuel rails at the rear of the carb bank.  A droop in the line in this first section can develop an air bubble that lets less fuel get by.

The issue isn't "no flow", it's "less than needed" flow.  The Valkyrie is very sensitive to this.  Just about anything the causes the slightest reduction in flow such as a droop in the line or most in-line fuel filters,  will result in fuel starvation at high speeds, particularly in the forward carbs.  It usually doesn't show up until 3 to 4 gallons of fuel have been burned, reducing head pressure that assists in pushing fuel all the way through the lines and fuel rails.

[Lyle Laun]

I recently had my carbs out for a cleaning and installed a slightly larger ID fuel line that was 1.5 inches longer than the old one just to make it easier to install. I also switched to a Pingel and the claim was that it flowed 3 times as much fuel as a stock Petcock. So far I haven't seen any issues.
Just wondering if the bigger ID of the hose and Pingel innards is letting me get away with the extra length ?

[ecw]

I searched through the forums and found cases of fuel line getting pinched, carb vent line getting pinched, defective fuel line components...  Seems like those are the big concerns.

A sag in the fuel line is not like "making the fuel flow up hill," even though it might seem that way.  The additional elevation drop to the bottom of the fuel line provides additional energy that exactly balances out the "up hill" portion of the fuel line.

[Willow]

I searched through the forums and found cases of fuel line getting pinched, carb vent line getting pinched, defective fuel line components...  Seems like those are the big concerns.

A sag in the fuel line is not like "making the fuel flow up hill," even though it might seem that way.  The additional elevation drop to the bottom of the fuel line provides additional energy that exactly balances out the "up hill" portion of the fuel line.

You go ahead and experiment where you think people have been in error.  Let us know if you're able to prove us all incorrect.

When a fuel line over the top of the engine gets a little warm and develops an air bubble you'll want that fuel line shorter again.

I suspect that issue could be solved were one to switch to a different fuel line material.

[Tx Bohemian]

Hey,

All this talk about tanks and fuel lines running up hill, what about bike that install the "extra" tanks?  Aren't these tanks installed in the space in front of the rear wheel?  And that's below the engine, not just the carbs, right? Or do these have fuel pumps?
Or am I off in left field here?

[Valkpilot]

Hey,

All this talk about tanks and fuel lines running up hill, what about bike that install the "extra" tanks?  Aren't these tanks installed in the space in front of the rear wheel?  And that's below the engine, not just the carbs, right? Or do these have fuel pumps?
Or am I off in left field here?

They have a fuel pump.  The main tank drains to the belly tank, which pumps to the carbs.

[Willow]

Hey,

All this talk about tanks and fuel lines running up hill, what about bike that install the "extra" tanks?  Aren't these tanks installed in the space in front of the rear wheel?  And that's below the engine, not just the carbs, right? Or do these have fuel pumps?
Or am I off in left field here?

Yes, but it's innocent enough.  Folks listen too much to terms like uphill and downhill.  People using those terms are just trying to explain why in their own understanding.  Whatever the cause the real issue is an air bubble in the gravity fed line and it tends to manifest itself with extra gas line.   

[GPz1100]

if i do replace the fuel line i was thinking 1/2" to 1" max. is that going to cause problems?

[The emperor has no clothes]

if i do replace the fuel line i was thinking 1/2" to 1" max. is that going to cause problems?

I don't think that will be a problem. But if it is you can always cut some off.  I've gotten used to the short fuel line. When removing the tank just raise the back enough to get your screw driver in there and loosen the clamp. On my I/S the previous owner added about 2" to the line and you could see where it was pinched down in a turn of the line. It never created a problem but I think after more time it might have.

[ecw]

You go ahead and experiment where you think people have been in error.  Let us know if you're able to prove us all incorrect.

Hmm... I've done it on my bike already, and searching the forum for past history found several others that have also succeeded.  As for "proving" it, I hope this isn't that big of a deal.