fuel starvation

[hillbillybiker]

Ok Guys need some help here.I can`t fiqure out why my fuel won`t flow right.Its a 67 flh with an S&S super E the tanks are clean with a new petcock new lines new filter.Breather cap is clear tank crossover is clear.But the fuel just dribbles and it can`t keep up with the engine and i run out in slow town traffic.Its really starting to piss me off its kick only and stalling in traffic is getting old any ideas i`m at a loss.i`ve tried everything i can think of.thanks..steve

[vern]

pull the hose of the carb and see how it flows. that way you'll know which way the problem is

[monty101]

I had problems several different times. Once because of alcohol mixed in the gas I  it was vapor locking because I had ran the fuel line between the jugs and the line got hot. I moved the line back under the oil tank and it quit vapor locking. Then I had problems with gas just not running out the line at the carb even though it appeared to be running out the filter when I pulled the line off the filter. I took the filter apart and it had fine bits of rust in it and I blew that out and the fuel ran out the line at the carb like it should and all is well now. I'm betting its the filter because mine looked like gas was coming out it but it evidently will fool you because it barely came out the line at the carb until I cleaned the filter then it shot out the line at the carb like it should.

[76shuvlinoff]

 Is this condition only when the engine is hot or cold too?  Gotta insulate that line from the heat of the heads.

[70weight]

Is your vent cap workin?

[easyricer]

You might take a air hose and blow out all of your hoses. Also pull the petcock and rinse the screen. A new petcock is only about $12 might just put a new one in just for the fun of it. You should get a pint of fuel in one minute or less out of a good petcock. (i think a Pingel will flow a gallon in a minute)
EASY

[Trouble]

I hope you're not running one of those in-line filters. The petcock filter is good enough. Make sure the fuel line does not touch the cylinder fins either.

[flhswingarm]

I seen the use of tank sealer partially block the outlets............ Yep I done it........had to ream the outlets with a wire

[pappyfreebird]

ony udda thing nawt mentioned would be float stickin in upward position nawt lettin it fill proper..a tap on bowl will cure that usually..them lil filters r trickie lil fuggars too..dont trust by lookin thru it either..keep us posted on the find

[hillbillybiker]

Ok.Its been doing it hot or cold Vent cap is clear,tank crossover is clear,lines are clear.I put a new petcock in but it came with no screen so i have an inline.which i just replaced again with another new one.It flows ok now but its done that before then it runs out and i have to wait for it to refill or sometimes blow in the tank to get it goin.I don`t use any tank sealer.What in the carb could cause it too do this any ideas?Well i went through it all again time for a test ride i`ll let you know.Thanks.Steve

[76shuvlinoff]

  Those in line filters have been brought up here before about collecting heat, I read reports of folks watching the gas boil in them.

   I know you've been down this road but to me it screams of a venting or crossover issue.

  Good luck

[MMOCGuy]

Two things I can think of.

First, as 76 said, your symptoms scream of crossover or vent issues.

Second, the only other thing I can think of is sticking float or sticking needle valve in the carb or a piece of something in the carb fuel intake restricting the flow of fuel through the fuel inlet. I have seen needle valves stick even when the float drops away. When that happens, it will either restrict the flow or stop it completely. In my experience, the only sure fix was to replace the needle valve.

Be absolutely certain that the vent crossover between the two tanks under the dash is not kinked and is absolutely free. Once you are sure of that, reroute your fuel line away from the cylinders and see if that helps. I would take a long piece of fuel line and route it around the front of the tank to the carb just as a test. Lastly, if both of the above check OK and you are still experiencing the problem, pull the carb apart and make sure the float or needle valve isn't sticking and that there isn't any little pieces of dirt or sealer stuck in the fuel inlet.

I hope this helps.

Norm.

[springer-]

Get rid of the in-line fuel filter.  Make sure the fuel line runs equally between the cylinders and does not touch the cylinders.  Ideally 2 inches away from the either cylinder. 

[hillbillybiker]

Well I made it 5 blocks.I checked the crossover twice the hose under the dash is also new.Just pulled the line off the carb now it flows fine what the hell

[MMOCGuy]

If I understand correctly, you made it 5 blocks and it quit? Then when you pulled the fuel line it flowed fine? If that is the case, your problem has to be in the carb.

Norm.

[hillbillybiker]

it must be but where

[Ultrashovel]

Ok.Its been doing it hot or cold Vent cap is clear,tank crossover is clear,lines are clear.I put a new petcock in but it came with no screen so i have an inline.which i just replaced again with another new one.It flows ok now but its done that before then it runs out and i have to wait for it to refill or sometimes blow in the tank to get it goin.I don`t use any tank sealer.What in the carb could cause it too do this any ideas?Well i went through it all again time for a test ride i`ll let you know.Thanks.Steve

You really need a screen on the petcock. I don't know what type of petcock you have but the stock ones aren't much good. I mean the ones that use the rubber disc for a gasket. I had nothing but trouble with fuel starvation on my Shovelhead until I bought a Pingel petcock. They are the best, IMHO.

[springer-]

Well I made it 5 blocks.I checked the crossover twice the hose under the dash is also new.Just pulled the line off the carb now it flows fine what the hell

If you still have the in-line fuel filter on and it is in between the cylinders or heads, you will chase your tail forever until you remove it.  I did the same thing about 15 years ago.  The bike would run great for a short distance or at low speed and then act like it ran out of gas.  When I pulled the line, the fuel would run out no problem.  The in-line fuel filter would heat up and cause vapor lock and prevent the fuel from flowing.  The second you stopped the bike and pulled the line, the filter was cooled enough to flow like a champ.

In-line fuel filters are for cars, not bikes.  Why so reluctant to at give it a try?  It takes 2 minutes to put a piece of fuel line direct from the petcock to the carb.  If it doesn't solve the problem, you can always put it back.  Remember, always do the simple stuff first.  This is simple compared to pulling your carb apart.

Good luck

[MMOCGuy]

Hillbilly.

I'd say that the problem is a sticking float, a needle valve that is sticking in its seat or there is a restriction in the fuel intake between where the fuel hose connects to the carb and the float needle seat.

I hope this helps.

Norm.

[1711tab]

pull the hose of the carb and see how it flows. that way you'll know which way the problem is

Posted on: Yesterday at 04:22:43 PM Posted by: springer- 

Get rid of the in-line 


If it flows with the in-line fuel filter on it then the filter sure as heck isn't your problem... It has to be in the carb...

[springer-]

pull the hose of the carb and see how it flows. that way you'll know which way the problem is

Posted on: Yesterday at 04:22:43 PM Posted by: springer- 

Get rid of the in-line 


If it flows with the in-line fuel filter on it then the filter sure as heck isn't your problem... It has to be in the carb...

You seemed to have missed the point about the in-line fuel filters.  It is not whether they flow or not but whether they flow when heated from being between the cylinders.  The only way to test for this is to remove the heat at the fuel filter from being the possible cause.  The easiest way to do that is to just remove the filter itself and see if the problem continues.  If the problem continues then yes, continue on looking for the source of the problem.

It could certainly be a float or needle valve sticking or a plugged jet or any number of other issues.  In my PERSONAL experience, having seen this exact problem several times before, when ever I see mention of an in-line fuel filter it becomes the first suspect.  And it is the easiest thing to rule out.  Troubleshooting this will be a process of elimination, why not eliminate the easiest thing to get to first?  If your bike doesn't start do you tear the engine apart first or check to see if it has fuel first?  Same theory here.

Many of the inline fuel filters are made of metal or glass and neither of those insulate the heat and cause vapor lock.  If the fuel filter is metal or glass it is the first thing I would suspect.  Some examples....

Bad...


More bad...


Better but I wouldn't want it melting if it came in contact with my cylinders and possibly spilling gas all over the hot engine I am riding on.

[springer-]

Ok Guys need some help here.I can`t fiqure out why my fuel won`t flow right.Its a 67 flh with an S&S super E the tanks are clean with a new petcock new lines new filter.Breather cap is clear tank crossover is clear.But the fuel just dribbles and it can`t keep up with the engine and i run out in slow town traffic.Its really starting to piss me off its kick only and stalling in traffic is getting old any ideas i`m at a loss.i`ve tried everything i can think of.thanks..steve

Additionally, in re-reading your first post and just noticing it has a S&S "E" carb, the fuel line enters the carb from the bottom, straight up.  Because of this, if the fuel line it a little long it will rest directly between the base of the cylinders and can heat up the fuel line also causing vapor lock.  Make sure the fuel line is not resting on any part of the hot engine.  Are you using the hose that comes with the carb?  It would have had a preformed bend in it to help prevent this from happening.  Note the hose on the bottom left of the picture...

Harley also knew this to be a problem and on stock bikes they had additional protection using a piece of shielding for the fuel line.  Note in the picture below, on the lower right, the piece of shielding that is supplied for the fuel line where it goes between the cylinders.  This is additional protection from heat.

[MMOCGuy]

Hillbilly

The two above posts by 1711 and Springer are good. The way I've been reading your questions and posts led me to believe that you have already eliminated the possibility of vapor lock by rerouting the hose and eliminating - at least temporarily - the fuel filter. If you haven't yet done these things, then, by all means, do them FIRST. Always check the easy stuff first.

Hope this helps.

Norm.

[pappyfreebird]

5 blocks is bout far as git wid the gas off...meaning float bowl runs empty...like said above elimenation...filter ,,make sure lines in right place..ifn nawt it ,,then its in yer bowl...sumthin stoppin its full flow (needle er lil bit a crap blockin)..thats wud id do anyways...mebbe evin low float setting ,,have you done anythin ta that??? low float level will cause this too...

[springer-]

You might also try driving with the gas cap loose.  If the vent in the cap lets air out and not in, it could also create vapor lock causing poor fuel flow.