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I always loop my fuel lines down between the jugs and up from the bottom to the carb. Keeps the fuel line away from the heat of the cylinder heads.

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Discussion Starter · #22 ·
I always loop my fuel lines down between the jugs and up from the bottom to the carb. Keeps the fuel line away from the heat of the cylinder heads.

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I will also when I put it back together.

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I am bewildered, this will be long but I am going to try to include everything. my 91 FXRS, is completely stock and runs great until it doesn't. It runs well at low speed ( under 50 mph) but when I get on the highway it accelerates normaly up to 75 mph and then runs out of gas. I pull in the clutch, keep it running and pull over. after a short time it's fine so I ride around , go back to the highway and it does it again, everytime. I bought this bike last fall, it has 42,000 and had belonged to a woman and she had changed virtually nothing. the gaskets were leaking and it had a bad front motor mount. I took it to my indi shop that has a very well trained mechanic with a lot of FXR/EVO experience. He removed the heads and jugs, Said it looked like it was leaking air at the intake manifold, I had the heads and jugs powder coated, he the put in new rings, lapped the valves, reassembled everything and it ran great, until you get on the highway. He then rebuilt the carb, changed the fuel petcock. replaced the fuel line, and it run great, until I got on the hiway. I thought it might be the gas cap not venting so when it stalled I loosened the gas cap. no joy. after I restarted it I left the cap loose and rode a 5 mile circle and pulled back on the highway same thing. Has anyone had this experience? I need to get this sorted out, I love riding this old bike. So hopefully someone here can provide so insight.
Thank you all in advance.


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FXR Series Carb Rebuild (episode 1) - Bing video

My first checks would be...
1.) clogged filters in tank and fuel lines slowing fuel flow.
2.) Carburetor complete cleaning
3.) Float height adjustment

If anyone took the carburetor off recently and dropped it down instead of setting it down on the bench, the float height in the carb could of been bent, and bowl fuel level may be short level leading your engine to suffocate for fuel.
 

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I am bewildered, this will be long but I am going to try to include everything. my 91 FXRS, is completely stock and runs great until it doesn't. It runs well at low speed ( under 50 mph) but when I get on the highway it accelerates normaly up to 75 mph and then runs out of gas. I pull in the clutch, keep it running and pull over. after a short time it's fine so I ride around , go back to the highway and it does it again, everytime. I bought this bike last fall, it has 42,000 and had belonged to a woman and she had changed virtually nothing. the gaskets were leaking and it had a bad front motor mount. I took it to my indi shop that has a very well trained mechanic with a lot of FXR/EVO experience. He removed the heads and jugs, Said it looked like it was leaking air at the intake manifold, I had the heads and jugs powder coated, he the put in new rings, lapped the valves, reassembled everything and it ran great, until you get on the highway. He then rebuilt the carb, changed the fuel petcock. replaced the fuel line, and it run great, until I got on the hiway. I thought it might be the gas cap not venting so when it stalled I loosened the gas cap. no joy. after I restarted it I left the cap loose and rode a 5 mile circle and pulled back on the highway same thing. Has anyone had this experience? I need to get this sorted out, I love riding this old bike. So hopefully someone here can provide so insight.
Thank you all in advance.


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Yea too long get a new bike
 

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I am bewildered, this will be long but I am going to try to include everything. my 91 FXRS, is completely stock and runs great until it doesn't. It runs well at low speed ( under 50 mph) but when I get on the highway it accelerates normaly up to 75 mph and then runs out of gas. I pull in the clutch, keep it running and pull over. after a short time it's fine so I ride around , go back to the highway and it does it again, everytime. I bought this bike last fall, it has 42,000 and had belonged to a woman and she had changed virtually nothing. the gaskets were leaking and it had a bad front motor mount. I took it to my indi shop that has a very well trained mechanic with a lot of FXR/EVO experience. He removed the heads and jugs, Said it looked like it was leaking air at the intake manifold, I had the heads and jugs powder coated, he the put in new rings, lapped the valves, reassembled everything and it ran great, until you get on the highway. He then rebuilt the carb, changed the fuel petcock. replaced the fuel line, and it run great, until I got on the hiway. I thought it might be the gas cap not venting so when it stalled I loosened the gas cap. no joy. after I restarted it I left the cap loose and rode a 5 mile circle and pulled back on the highway same thing. Has anyone had this experience? I need to get this sorted out, I love riding this old bike. So hopefully someone here can provide so insight.
Thank you all in advance.


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Definitely sounds like a vapor lock in the fuel system.
 

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So how bout you vapour lock guys explain how a gravity feed fuel line vapor locks? Seriously, I'm interested to hear the mechanics of it.
 

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Discussion Starter · #28 ·
Yes there is a crack in the spigot and I ordered a new brass one with a barb fitting.

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So how bout you vapour lock guys explain how a gravity feed fuel line vapor locks? Seriously, I'm interested to hear the mechanics of it.
Gasoline has a boiling point starting as low as 95 deg F

When a fuel line rests up against the cylinder or head and heats to several hundred degrees in temp, the fuel inside the line can vaporize (boil) and prevent the majority of fuel from flowing. Usually a trickle at best gets through because the vapor causes back pressure in the line. I first learned about this many years ago when I put one of the glass see threw fuel filters in line, between the cylinders, of my first Harley. Turn the fuel on and it would fill and be gas colored. After riding my bike would die and I would pull over and could see no apparent problem. It would start right up and run fine again. When I got serious about fixing the issue we focused on the fuel system. We could see when it was running the fuel filter was almost clear and just a trickle of fuel was flowing. The glass filter was acting like a fuel oven and creating vapor lock. Once we figured it out, you could clearly see it. From that day forward in-line fuel filters were a huge no-no.

Years later, the same bike had the same problem however I didn't have an in-line fuel filter. It had a brand new set of tanks, new Pingel high flow petcock, new S&S E, new fuel line and a new engine. It would die on the highway once you hit about 60. Stop on side of road and check everything and no problems found. Start right up again and run great until you hit 60 for a couple minutes and it would die again. This time is it was the fuel line loop that was resting against the cylinders at the bottom of the "V" between the cylinders. I shortened the line and raised it up so it wasn't touching and it never happened again.

Gravity feed or not, the heated fuel line will cause vapor in the line and not supply the bowl enough to keep it running under a load. I've seen it many times since then and in nearly every instance removing fuel filters and/or moving the fuel line solved the problem. However looking at the pictures he posted, that doesn't appear to be the problem here.
 

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Discussion Starter · #30 ·
I went to the local Dealer and bought a carb kit and a brass elbow. I already have a new petcock. It has been awhile since I rebuilt a carb, but it is something I can do on the bench and not the floor. just need carb cleaner and a new fuel line and clamps. and maybe a few cold snacks.

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When you say it seems to run out of gas, do you mean it dies and goes and dies and goes?
Or does it just die?

I seem to remember something about an electrical component (coil?) that was failing when hot and working when cooled off.
 

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I went to the local Dealer and bought a carb kit and a brass elbow. I already have a new petcock. It has been awhile since I rebuilt a carb, but it is something I can do on the bench and not the floor. just need carb cleaner and a new fuel line and clamps. and maybe a few cold snacks.

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Jets are inexpensive and can be difficult to clean. If you're going into the carburetor I'd replace rather than try to clean them. At least the pilot jet, float and needle valve.
 

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30 plus years ago, a guy brought in his EVO bagger to my friends shop.
Bike would fall on its face when getting up to speed. Looked in the carb and if memory serves me correctly, found that someone had already been in there and the metering rod hanging from the slide was installed upside down. Cutting off the fuel. Not saying this is your fix, but keep an eye out for it. And make sure your float height is correct.
 

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Discussion Starter · #34 ·
When you say it seems to run out of gas, do you mean it dies and goes and dies and goes?
Or does it just die?

I seem to remember something about an electrical component (coil?) that was failing when hot and working when cooled off.
It loses power, sputters, If I pull in the clutch I can keep it running, when I stop it will idle fine, and then run normaly until I bring it back to about 70 MPH. It will run fine all day as long as I don't rip on it.

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Discussion Starter · #35 ·
The rebuild kit I bought did not come with a new float and the dealer parts guy said that it was discontinued. They seem to be available in the web tho. I may order one there because I want a new one. may buy a jet kit also just to cover all the bases. Am I forgetting anything?

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Fuel supply,, ignition coil, and the sensor plate , all can cause the bike to quit running,,, the 2 electrical components usually require more time to cool off than this bike exhibits..

The carb jets can be the issue,,, however, the passages the jets feed fuel and air through are more frequently the issue,, in the manyhundreds or probably thousands of carbs I have taken care of the issues,,, this fuel we use,, dries concrete,,, carb cleaner and compressed air, do not break this up..
Anymore,, I pull the CV carb, take it apart, use an .015" pin vise drill to open the passages,, then carb cleaner and compressed air,,, I have enough experience not to damage the carb with the drill bits.. it take a gentle touch and patience, something I do not possess either of these,,
 

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Discussion Starter · #37 ·
Looks like I need a pin vise and bit set to my list.

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Gasoline has a boiling point starting as low as 95 deg F

When a fuel line rests up against the cylinder or head and heats to several hundred degrees in temp, the fuel inside the line can vaporize (boil) and prevent the majority of fuel from flowing. Usually a trickle at best gets through because the vapor causes back pressure in the line. I first learned about this many years ago when I put one of the glass see threw fuel filters in line, between the cylinders, of my first Harley. Turn the fuel on and it would fill and be gas colored. After riding my bike would die and I would pull over and could see no apparent problem. It would start right up and run fine again. When I got serious about fixing the issue we focused on the fuel system. We could see when it was running the fuel filter was almost clear and just a trickle of fuel was flowing. The glass filter was acting like a fuel oven and creating vapor lock. Once we figured it out, you could clearly see it. From that day forward in-line fuel filters were a huge no-no.

Years later, the same bike had the same problem however I didn't have an in-line fuel filter. It had a brand new set of tanks, new Pingel high flow petcock, new S&S E, new fuel line and a new engine. It would die on the highway once you hit about 60. Stop on side of road and check everything and no problems found. Start right up again and run great until you hit 60 for a couple minutes and it would die again. This time is it was the fuel line loop that was resting against the cylinders at the bottom of the "V" between the cylinders. I shortened the line and raised it up so it wasn't touching and it never happened again.

Gravity feed or not, the heated fuel line will cause vapor in the line and not supply the bowl enough to keep it running under a load. I've seen it many times since then and in nearly every instance removing fuel filters and/or moving the fuel line solved the problem. However looking at the pictures he posted, that doesn't appear to be the problem here.

I've seen fuel boiling in clear fuel hoses on Harley's, with no vapor lock. It was surely reducing the flow, but not enough to limit the supply to the engine. With that said, lots of carb'd Harley's came with a little wire stand off to keep the line away from the jugs. And they usually seem to get lost pretty often. The biggest issue I have seen is with the S&S carb, and the fuel line entering from below. The vapour bubbles that do develop and travel to the carb side of the line, have to vent through the float valve. The shape of the fuel line run creates a vapor trap at the carb inlet. And that can starve the motor for fuel, as the fuel level in the line will always be below the vapour. In a proper setup, the fuel line will run up hill from the carb to the petcock. That way any bubbles will just vent back to the tank.
 

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It's them whore whips on your handlebar grips. LOL
Maybe there's some sediment in the bottom of the tank and petcock. Also wonder if it could be electrical, ignition get's hot and you lose a cylinder until it cools some. Had that happen years ago with a Crane HI 4.
[/QUOTE


Had the same thing happen with a Crane HI-4 on my '82 FXRS.
 

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"I've seen fuel boiling in clear fuel hoses on Harley's, with no vapor lock. It was surely reducing the flow, but not enough to limit the supply to the engine."
Never been able to ride, look at the road, and my fuel line at the same time. If you can, was the motor at cruise, or under load?
 
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