Running out of fuel

Yamaha_chop · Posted: April 2, 2009, 6:40 pm Post subject: Running out of fuel

hey guys, quick question here:

I'm running a sportster tank with one manual petcock that y-s into both carbs. I'm also running an inline clear plastic fuel filter.

Here's the problem; When I turn the fuel to "on" the plastic fuel filter fills with gas and the engine runs great, however, after running it for a little while the fuel level starts to drop in the filter. Eventually the gas runs out and the bike doesn't seem to be getting any fuel from the tank. If I stop the bike, turn off the gas and let it sit for awhile, then turn the gas back on, the fuel filter fills with gas again!

It's like the fuel line is getting vapor locked or something, and won't accept more gas until the bike cools for a bit.

Anyone experience anything like this?

any questions or things I left out that you need to know by all means ask away.

thanks
Sky

jayel · Posted: April 2, 2009, 6:45 pm Post subject: Re: Running out of fuel

check the gas cap vent, the tank is vapor locking not the filter... some of the later H-D tanks have a vent tube into the tank if it has one of them make sure it isn't plugged

xsjohn · Posted: April 2, 2009, 6:46 pm Post subject: Re: Running out of fuel

Does it do that withthe gas cap loosened..........xsjohn

Yamaha_chop · Posted: April 2, 2009, 7:04 pm Post subject: Re: Running out of fuel

Yes I did think of that, I took the cap off completely, same deal. And I made sure the vent itself was clear as well.

appreciate the quick replies guys...

oldskoolcool · Full Member Joined: Sep 08, 2007 Posts: 372

take the filter out and try. i have had filters cause problems.

Yamaha_chop · Posted: April 2, 2009, 7:25 pm Post subject: Re: Running out of fuel

I changed the filter to a new one just a few days ago, but it is a super cheap style of filter. Maybe I should replace the filter with a short length of clear tubing, that way I can see if there's still a problem or not.

pamcopete · Posted: April 2, 2009, 7:43 pm Post subject: Re: Running out of fuel

some filters work too good, especially when the tank gets low. The only way to be sure is to drain the fuel from the tank through the filter in the prime position of the pet c***, which gets the fuel from the same drain tube as the reserve, then check if all the gas is gone.

Also, some filters are designed to work with a fule pump, so they are not suitable for the XS650.

xjwmx · Posted: April 2, 2009, 7:46 pm Post subject: Re: Running out of fuel

Make sure the arrow in the filter is pointing toward the carb. Make sure all of the line is lower than the tank.

It sounds like a kink in the line that passes fuel slower than the bike burns it up, but it's probably not. I'd make the problem happen, then take the hose loose from the valve and see if gas then came out of it. If so, plug it back in, and see what happens in the filter. Connect a tube to the bowl drain and make sure it flows into the bowls. Also - a half empty gas tank can cause some strange symptoms. The problem can only be very few things. Make sure each thing is working right, and it will all work.

Yamaha_chop · Posted: April 2, 2009, 8:51 pm Post subject: Re: Running out of fuel

xjwmx wrote:

Make sure the arrow in the filter is pointing toward the carb. Make sure all of the line is lower than the tank.

It sounds like a kink in the line that passes fuel slower than the bike burns it up, but it's probably not.

Filter is in correctly, all line is lower than the tank. The lines are bent at fairly extreme angles to get into the carbs, but it's wierd that it seems to work for a short time.

Here's a quick picture of the current setup:

thanks again for all the great suggestions guys.

xjwmx · Posted: April 2, 2009, 9:13 pm Post subject: Re: Running out of fuel

Yamaha_chop wrote:

The lines are bent at fairly extreme angles to get into the carbs, but it's wierd that it seems to work for a short time.

Well, if it did happen to be a constriction in the hose, you have a rate of flow out of the jets, and also a rate of flow into the bowl that's governed by the constriction. If the rate of flow into the bowl was the right amount less than the rate of flow out of the jets, then you'd see what you're seeing (if the constriction or obsruction is before the filter) as the filter and bowl slowly emptied. Then with the bike off, both would slowly fill again. Hold the angles straighter as a test and see what happens. Take the downstream side of the filter loose, and make sure gas is just pouring out of it, like it should. If not, then it's the filter or petcock or something in the tank.

I have a clear filter in mine, and the petcock must have a slow leak, because in the morning the filter will be nearly full, but when it's run awhile, there's just a little bit of gas visible. But it always gets enough gas. I don't know why my filter isn't full all the time, since it's lower than the tank, but it's working.

weekendrider · Posted: April 2, 2009, 9:25 pm Post subject: Re: Running out of fuel

Oregon makes a fuel line you can see through. You can find it at small engine/chainsaw shops. That make it easier to track the flow?

gordo · Posted: April 2, 2009, 10:02 pm Post subject: Re: Running out of fuel

Hey Chop, is there a screen in the petcock itself? Or maybe there is something floating around in there or the tank blocking fuel flow.

jayel · Posted: April 2, 2009, 10:24 pm Post subject: Re: Running out of fuel

simple test.... pull the hose off your tee and run it into a gas can for 5 minutes or how ever long "engine run a little while" is, see if it slows and stops or if it flow freely the whole time, I'm still betting on the tank vapor locking, that petcock will supply enough fuel for a 1200cc Sportster it ought to supply a 650cc

bluebikerblan · Posted: April 2, 2009, 11:13 pm Post subject: Re: Running out of fuel

Just a shot along the lines Jayel is working......as I look at that tank and from what I recall of H-D tanks isn't there a cross-over tank flow tube which is supposed to keep the fuel level equal on both sides of the tank even though you're drawing off only one side? That tank is tilted to the rear quite a bit as well. You're going to have quite a bit of gas left below the level of the tank exit level.
If it's getting low on the exit side of the divided tank tunnel it could be frothing at the petcock level even when you think you have plenty of fuel. It's also on the uphill side (opposite of the sidestand) Cross over flow tube. Do you have one? Is it clear and running under the tube & tunnel?

Best, Blue

MN_TX650 · Full Member Joined: Jul 17, 2008 Posts: 331

I may be wrong, but that filter looks fairly perpendicular which may cause your problem. Gravity isn't pulling it as much as it would more vertical? Seems like a logical problem to me. I would attempt to get the flow of fuel more vertical if possible...atleast at the filter.

tacoswild · Posted: April 3, 2009, 11:33 am Post subject: Re: Running out of fuel

I had a similar paper filter in a similar layout and I would stop getting fuel long before I hit the reserve level of the tank. Took it out and no more problems. Some people run them successfully, don't know what their secret is, mine had to go and a less restrictive filter is in there now.

MN_TX650 · Full Member Joined: Jul 17, 2008 Posts: 331

I am running something similar to these on mine: www.jcwhitney.com/Fuel..._10111.jcw

woodman · Full Member Joined: Oct 12, 2008 Posts: 256

Big Harleys like my Fatboy have the cross over fuel line but Ive never seen one on a Sportster. Have you looked at the screens on the petcock up inside the tank ? Dont some of the Specials 80 on have a screen under the needle seat ? I could be wrong but I thought they did.

Yamaha_chop · Posted: April 3, 2009, 2:10 pm Post subject: Re: Running out of fuel

Yeah there's no crossover line on these tanks. Definitely with the way it's been mounted there's a fair amount of fuel in the tank that will never make it out Smile

I'm going to try draining the tank after the filter to determine if the problem is coming from that end or not. If it flows fine then I can at least narrow it down a bit.

Thanks again everyone.
Sky

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