Fuel line air bubble

[Idealistmeb]

Help! I have a 1980 special and I am having trouble with getting air bubbles in the fuel line. I have tried to get the fuel line full with no bubbles before I go on a ride and it runs great for 10 miles or so, then I notice it starts to run rough. It has large air bubbles in the fuel lines and it seems like it is not getting the gas it needs to run properly. Any help or ideas of what to look for would be greatly appreciated.

[mack]

Are

you running it with the octy ? Where exactly is the air bubble? Is it on both feeds? The only way for air to get into the fuel line is a loose connection or if the bike sits for a few hours you would notice a gap in the fuel line from evaporation through the carb vent holes located in the bells, but once the motor is running again the fuel fills the lines within a few seconds. How is the flow from your petcocks? Does it do it if you have it on prime?

[mack]

The

other thing you may want to check if the bubble is in both lines is your gas cap vent. It's possible to starve the carbs if the vent is plugged and the fuel isn't flowing properly. Quick check is to run the bike your ten miles with the cap on loose and see if it solves the problem.

[Idealistmeb]

I took the October thing off and am running fuel lines from the petcock from the left side to carbs 3&4 and from the right side to carbs 1&2. Both lines have an in line fuel filter. The bubble usually is formed after the filter. All the lines are tight where they connect. I will check the gas cap and see if that helps. I will check the petcock flow also.

[donebysunday]

Check

, make sure it's air. I had one that looked like air in the line, could not get it to move. I cut the line right in the middle of this bubble and it was like vaseline.
This was old ethanol fuel residue, tank sat on the shelf for 3 weeks, an entire bottle of chevron techron ( not the weaker chevron with techron ). The chevron techron with a full tank of non-ethanol fuel

Help! I have a 1980 special and I am having trouble with getting air bubbles in the fuel line. I have tried to get the fuel line full with no bubbles before I go on a ride and it runs great for 10 miles or so, then I notice it starts to run rough. It has large air bubbles in the fuel lines and it seems like it is not getting the gas it needs to run properly. Any help or ideas of what to look for would be greatly appreciated.

[mack]

If

you still have the symptoms after checking it with a loose gas cap, take the fuel filters out and try it without them.

[Idealistmeb]

Ok here is what I've done so far. I removed and cleaned the petcocks and noticed the in-tank filters were not seated properly, (half in and tilted). I fixed those and now I seam to have good flow from the tank. I went for another ride and still more air than gas in the line. when the fuel line is connected to the carbs there is no/little flow of gas. When I take it off the carb the gas flows fine.

I then decided to take off the in-line fuel filters and went for another 20 miles. I have more gas than air in the line but still runs rough and seams to have a vapor lock when connected to the carbs. This is the case for both lines from the petcocks. Is there a vent on the carbs that could be clogged/blocked? or could it be something else?

[mack]

The

carb bowls are vented through the bells. It's possible. are you running an air box or pods?

[Idealistmeb]

I have pods on them with a small section of PVC pipe attached to correct for the blocking of the air jets.

[mack]

might

be a good Idea to double check the fit and ensure the vents aren't blocked. I don't use pods but I know from other threads that this is a common issue with some of the pods out there. Perhaps someone else with pods can chime in at this point.

[TopCatGr58]

Hey there Idealist,

I have a modified 81SH as well, have PODS with the PVC velocity stacks, work fine.
I also have inline little lawnmower style fuel filters. There IS air in the lines, it's not critical at all....fuel will flow thru the lines and the air won't block the flow. The diameter of the fuel lines are big enough to not allow the air to create enough surface tension in the fuel around it to prevent the flow of fuel.

Mine have been working fine for years, but this fall during a rally, I was having problems once I had to switch to reserve, it didn't help, and had to stop for fuel ASAP. Once topped off, it would work okay again until the fuel ran low. I finally experienced a severe fuel flow problem that occured with only 2 gallons of fuel used instead of the usual 3.5 gallons that would usually get used before hitting reserve. Stopped at a auto parts store and pulled the filters off..one blew thru easily, the other was rather restricted. Replaced with new free flowing one, and the bike worked fine again.

Okay, reread your replies, fuel flows from petcocks,thru lines with or without inline filters when NOT connected to the carbs, but the carbs still seem to not be getting enough fuel. Gas cap vent is clear.

The carbs have a screen under the float needle VALVE assembly, and it can get clogged and restrict flow. I don't remember you saying whether you have cleaned the carbs or what you have done to them?? Also, the fuel inlet "T"s can get clogged/corroded/gummed up as well. As was stated, the later carbs float bowls are vented thru the inlet bell, that's what the 4th port in them is vs. the earlier carbs that only have 3 ports, but have an extra "T" fitting up higher on the carb body for their vent.

T.C.

[skids]

I posted once before on this. There are chemicals that can increase the surface tension of fuel. I am not sure if it was the Caswell's tank liner (done properly and completely cured), the Techron fuel system cleaner, or what. I pulled the petcocks and there was standing fuel trapped in the filter towers. That was a long time ago, but I still need to switch to reserve it seems long before I should on the standard. :-/

[Idealistmeb]

TC, The problem I'm having is that there seems to be limited gas flow to the carbs not necessarily bubbles in the line. I can have the line completely full of fuel and go for a 10 mile ride and have very little gas in the line. It still runs but rough. It has been about a year since the carbs have been cleaned. So I should take them apart and do a thorough cleaning.

Is there something I should be looking for specifically that could cause the problem I'm having when I'm cleaning the carbs? I will make sure the bell vents are open and venting, other than that, any suggestions?

[TopCatGr58]

Is there something I should be looking for specifically that could cause the problem I'm having when I'm cleaning the carbs?

Just what I said earlier.

The carbs have a screen under the float needle VALVE assembly, and it can get clogged and restrict flow. Also, the fuel inlet "T"s can get clogged/corroded/gummed up as well.

T.C.

[Rasputin]

I can have the line completely full of fuel and go for a 10 mile ride and have very little gas in the line. It still runs but rough.

If there is no fuel getting into the line your problem is in the tank or the petcocks. No amount of carb rebuilding will help that. I would disconnect your fuel lines and let them run wide open into a pail or other container and see what is happening there, long before pulling carbs. If it is very slow then open the gas cap and see if that changes things, I doubt it will.
As TC says that little screen needs to have its full share of attention when cleaning carbs, but if fuel is not getting to that screen it will not matter.
Also air bubbles in the fuel line mean absolutely nothing to how the bike will run. If it bothers you just install black lines and you will never know if there is an air bubble. Depending on how you route the lines they may always have air in them. I ave a bike that has had bubbles in the line for years and it still runs great.