fuel stops flowing

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MexicanMafia
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fuel stops flowing

#1 Unread post by MexicanMafia » Sun Feb 03, 2008 11:25 am

so now i got the bike running again i have a problem with the fuel flow. it'll do good for about 20 mins of riding or so, and then the fuel will stop flowing thru the lines. i can see it stop thru my inilne filter. so i took the tank off and cleaned it out. check the petcock, it's good and flows good. so now my only guess is a stuck float but i just went thru the carbs and check the float valve and the housing and it all looked good with lil to no ridges on the rubber points. anything else that could be causing it to stop flowing.


i can blow thru the lines and then hook it back up and it'll start goin again. would this indicate a stuck float?? thanks.

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#2 Unread post by Johnj » Sun Feb 03, 2008 12:26 pm

Sounds like your fuel tank vent is plugged. Try riding until the bike dies. Open the tank. Do you hear a hissing noise as the tank opened? Close the tank and try to start the bike.
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#3 Unread post by storysunfolding » Sun Feb 03, 2008 2:29 pm

Johnj wrote:Sounds like your fuel tank vent is plugged. Try riding until the bike dies. Open the tank. Do you hear a hissing noise as the tank opened? Close the tank and try to start the bike.
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#4 Unread post by MexicanMafia » Mon Feb 04, 2008 9:46 am

yea i do sometimes. but after i open it, it still won't flow. and if i don't open it and just pull the line off fuel will flow out of the petcock. also where is the tank vent for this, the other tube out of the petcock?? thanks.

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#5 Unread post by flynrider » Mon Feb 04, 2008 12:33 pm

You'll have to check a manual for the location of the tank vent. Many have a vent in the cap, but not all of them do. A clogged vent will prevent fuel from flowing out of the tank after it's been running normally for 10-20 min.

The fact that you see the fuel flow stopping in the line/filter, pretty much rules out the carb floats, doesn't it? The problem has to be in the tank, petcock or fuel line.

You mentioned that you have another tube going into the petcock. That would indicate that you have a vacuum operated petcock. If the vacuum line is leaking, it could restrict fuel flow. Also if the vacuum diaphram inside the petcock is damaged, same deal. Just about all vacuum petcocks have a position labeled "prime". You can bypass the vacuum function by using this setting. Next time the fuel stops flowing, put the petcock in the "prime" position. If you see the fuel start to flow, then your problem is likely in the vacuum line or the diaphram.
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#6 Unread post by MexicanMafia » Tue Feb 05, 2008 8:20 pm

i don't think it's the petcock casue when i unhook the line fuel with come out with tring to start the bike and stops when quit cranking it over. i can blow into the line goin to the carbs and hook it all back up it'll go for about 5 mins now and then stop flowing again. this is with the tank open too.



also there is no prime position, just off, on, and res

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#7 Unread post by Pongo » Wed Feb 06, 2008 10:07 am

flynrider wrote:Also if the vacuum diaphram inside the petcock is damaged, same deal.
I agree... But firstly remove and clean the vacuum diaphragm. If that doesn't work and it is damaged you will need to replace the whole diaphragm assembly as a unit.

Do you have a service manual?

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#8 Unread post by MexicanMafia » Wed Feb 06, 2008 11:50 am

yes i have a manual. i check the petcock a while ago and the diaphram and spring look good and new. i think it works too cause when i unplug the line and start it it'll flow fuel and then stop when i stop, jsut when the line is hooked up it'll only flow for a min. you think that there's more pressure in the line or something? thanks.

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#9 Unread post by Johnj » Wed Feb 06, 2008 12:24 pm

Still sounds like your tank isn't venting.



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#10 Unread post by MexicanMafia » Thu Feb 07, 2008 8:22 am

MexicanMafia wrote:i don't think it's the petcock casue when i unhook the line fuel with come out with tring to start the bike and stops when quit cranking it over. i can blow into the line goin to the carbs and hook it all back up it'll go for about 5 mins now and then stop flowing again. this is with the tank open too.



also there is no prime position, just off, on, and res

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#11 Unread post by Johnj » Thu Feb 07, 2008 10:50 am

OK try this. Get a fuel tank off an old lawn mower. Get 3 feet of ¼inch hose, a ¼inch connector, and an in-line fuel filter. Cut the hose in two so you have a 1 foot and a 2 foot section. Install the filter with the 1 foot section to the inlet and the 2 foot section on the outlet. Place the short hose to the tank and the ¼inch connector on the other end. (I used a plastic ¼inch shut-off valve from a plumbing supply store instead.) Now you have a small tank that you can test with.

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Use this to test your tank. If you can run one of these dry the problem is your tank. If you can't replace the hose between the tank, including the fuel filter, to the carbs.


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#12 Unread post by MexicanMafia » Thu Feb 07, 2008 4:16 pm

cool, you think that a 1 gallon gas can will do the same thing?? thanks.

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#13 Unread post by Johnj » Fri Feb 08, 2008 12:43 am

No, a 1 gallon gas can doesn't have anyway to connect a hose. Get a tank off a push lawn mower.
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#14 Unread post by XJRJohn » Fri Feb 08, 2008 2:43 pm

Just a thought,but are you sure theres somthing wrong with the fuel lines?When the carbs are full the fuel will flow slowly and through an in line filter will appear to have stopped flowing.Run the bike till it cuts out and fuel stops flowing ,then open the overflow on the bottom of one of the carbs and if fuel comes through youre still getting fuel.You might then have to look somewhere else for the problem.xjrjohn
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#15 Unread post by techyguru » Wed Feb 13, 2008 12:43 pm

When you say you can see it stop flowing, do you mean that there is still gas there but it isn't moving, or the gas is leaving the line and it becomes empty?

If the gas is still present and just stationary, the problem may be due to a blockage in the carbs or something else stalling out the bike. In this case the engine wouldn't be using any gas so it would stop moving.

If the fuel line is empty of all gas I would suspect a problem before the line.

The other possibility is your gas line is air tight and thus it cannot empty out, in which case it could be a blockage before or after the line.

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