[sumdatx]

I would bet that you need the correct petcock. At those speeds you mentioned, you're sucking a lot of fuel. I remember my first trip on my 1300. Around here I routinely got around 45mpg. After my first fuel stop on the super-slab, I was only getting 33mpg. Doing 70-75 mph which is loafering today.
Take a peek at Partzilla.com and look at the parts fiche. Compare your tank with a newer model (05, 06). I know the petcock assy is costly, but you might find one on Evil-bay -- just to try.
I messed up my original tank and got a second hand one. My friend and I took a sawzall to the old tank, cut it in half. I wanted to see what was inside That vent line was really hard to understand. It was routed from the rear of the tank in an "S" pattern along the top of the tank to a small rectangular metal box at the front of tank in front of the filler neck. Looked like a solid box to me......strange vent system
Long winded post here, but wanted to share.
tom

 

[Vinish]

Sorry about my bad petcock advice. I did not see that it was a 2003. So, do you have a petcock with no "guts" (diaphragm, spring, etc.)? If so, that seems an unlikely place for the fuel to be restricted.

 

[Silver F]

the flow rate should NOT change with the bowl on or off..
air is to excape while the fuel enters.

 

[SharpAndCunning]

I would bet that you need the correct petcock. At those speeds you mentioned, you're sucking a lot of fuel. I remember my first trip on my 1300. Around here I routinely got around 45mpg. After my first fuel stop on the super-slab, I was only getting 33mpg. Doing 70-75 mph which is loafering today.
Take a peek at Partzilla.com and look at the parts fiche. Compare your tank with a newer model (05, 06). I know the petcock assy is costly, but you might find one on Evil-bay -- just to try.
I messed up my original tank and got a second hand one. My friend and I took a sawzall to the old tank, cut it in half. I wanted to see what was inside That vent line was really hard to understand. It was routed from the rear of the tank in an "S" pattern along the top of the tank to a small rectangular metal box at the front of tank in front of the filler neck. Looked like a solid box to me......strange vent system
Long winded post here, but wanted to share.
tom

Any chance you have any photo's of this? I'd like to see them, if for nothing else, just to learn. I guess,
I just don't understand how the petcock could be a problem. The vacuum actuated petcock simply allows fuel out of the tank when the engine is running, and not when it isn't, to prevent gas from leaking out of the petcock. It's a safety thing. If you know more about it, please let me know.

Sorry about my bad petcock advice. I did not see that it was a 2003. So, do you have a petcock with no "guts" (diaphragm, spring, etc.)? If so, that seems an unlikely place for the fuel to be restricted.

the flow rate should NOT change with the bowl on or off..
air is to excape while the fuel enters.

I remember testing the fuel flow at the end of the hose where it would connect to the carb, and it seemed to be a pretty steady flow. When I took the fuel bowl off last week and played around with the float/needle (for cleaning) but I wanted to see the flow, it seemed to dribble. Maybe there is an obsturction between the fuel inlet and where it goes into the bowl. I guess I can take it back apart an look.

I really and getting tired of taking this air cleaner assembly off. Those damn vacuum lines on the back of it are a pain in the ass. There, I said it.

Please don't appologize. I'm sorry If I come off disgruntled via text. I promise I am not trying to. I'm open to any and all suggestions.

 

[sumdatx]

I wish I had just a little experience with a VTX1300 that uses a fuel pump. But, it is what it is. I do have experience I wish I didn't have: chasing a problem and spending too much money buying too many parts that was not where the problem ended up being. I ended practically rebuilding my carb and I just needed to put the needle clip in the right slot .... As these VTX's get older and have been through a couple of different owners, it just gets more difficult to track down issues. I know you'll find the solution - the VTX is actually pretty simple to fix.
Have patience, be sure to keep a check list of everything you've looked at and eliminated.
tom

 

[sumdatx]

Just read your initial post again. Did you completely remove the fuel pump and the inline fuel filter ? I tried an inline fuel filter once and could not get good fuel flow to the carb - spit sputter. Gravity fuel feed rules out any extra filters. I do recommend you put the tiny screen filter back into the carb fuel inlet. You'd be surprised how much sandy junk it collects.
I'ma gonna check partzilla fiche and look for differences that may help solve this.
tom

 

[JPT]

As mentioned by Silver F earlier... Are you sure you don't have a partially clogged gas cap vent? If the bike is needing a lot of fuel and the vent only lets a little bit of air in to replace the fuel leaving, it will starve the carb of fuel.

I was riding on the highway and pulled over to help a fellow rider (on an enduro), this was his problem, as soon as he got up to speed the bike was stalling. I mentioned the tank vent, and he remembered he recently changed the cap. He was able to ride home with the cap loose.

 

[sumdatx]

Looks like your petcock is very different: has no vacuum port, just a fuel outlet. Suppose the fuel pump pulls enough fuel to the carb without need of vac, but going to gravity feed may create a fuel starvation issue. Have to compare a petcock from each kind to see for sure. 04-07 use the same gravity feed petcock with vac from manifold to a "t", from T to carb air cutoff valve and other side of the T to the petcock. The air cutoff valve and the accelerator pump (on the corner of the float bowl) both use a rubber diaphram. Just check for holes/cracks and seals ok.
Tom

 

[sumdatx]

The 1300 gas cap does not vent. 1800, yepper and I wished I could have used one but they're different. Since I am using a previously rusted tank, the VENT line was closed by rust, I ended up making a vented cap with a drill and progressively larger hole until it vented enough. There's a thin washer (?) on top of the rubber seal in the cap and it's has a little play. I drilled through a small section of the rubber and through that washer . Still seals enough so I don't get any gas leaking and I have a vent. Cost nothing to do vs $1500.00 for a new tank (at todays new tank pricing). Was around 1000.00 when I did this in 2016.

 

[sumdatx]

A little info from the OA: 1300 Carburator: Scar Mod, A/F Mix&Idle Adj, Fuel...

 

[SharpAndCunning]

I wish I had just a little experience with a VTX1300 that uses a fuel pump. But, it is what it is. I do have experience I wish I didn't have: chasing a problem and spending too much money buying too many parts that was not where the problem ended up being. I ended practically rebuilding my carb and I just needed to put the needle clip in the right slot .... As these VTX's get older and have been through a couple of different owners, it just gets more difficult to track down issues. I know you'll find the solution - the VTX is actually pretty simple to fix.
Have patience, be sure to keep a check list of everything you've looked at and eliminated.
tom

Thanks for that. I know when I checked the needle Diaphraghm, I made sure to the clip back where it was, when I got it. But who knows if that is correct.

Just read your initial post again. Did you completely remove the fuel pump and the inline fuel filter ? I tried an inline fuel filter once and could not get good fuel flow to the carb - spit sputter. Gravity fuel feed rules out any extra filters. I do recommend you put the tiny screen filter back into the carb fuel inlet. You'd be surprised how much sandy junk it collects.
I'ma gonna check partzilla fiche and look for differences that may help solve this.
tom

I completely disconnected the fuel pump and the inline filter. When the fuel pump is connected, the line runs from the petcock down under the seat, where the pump is, and then through the pump back up to the carb. I disconnected the electrical to the fuel pump, and "abandoned it in place". I ended up using a long piece of the fuel line from that setup to run from the petcock to the carb. It's a hard rubber (reinforced) line. The only part number I could find on it is 90---140317 08 05. It says its NBR + PVC. I found that typical fuel line kinked when routing from the petcock to the carb.

I realize the fuel strainer is probably a good idea, but I was trying to remove all fuel restrictions to the carb in an effort to figure out why the bike is behaving the way it is.

Looks like your petcock is very different: has no vacuum port, just a fuel outlet. Suppose the fuel pump pulls enough fuel to the carb without need of vac, but going to gravity feed may create a fuel starvation issue. Have to compare a petcock from each kind to see for sure. 04-07 use the same gravity feed petcock with vac from manifold to a "t", from T to carb air cutoff valve and other side of the T to the petcock. The air cutoff valve and the accelerator pump (on the corner of the float bowl) both use a rubber diaphram. Just check for holes/cracks and seals ok.
Tom

I don't know enough about the petcocks to say one way or another. I do know, there were threads on this and VTXOA about multiple members with 2003 VTX's and removing the fuel pump, going to gravity feed, without changing the petcock with success. I only removed the fuel pump per multiple recomendations on the forums, because of their tendency to fail, and the cost of replacement. I did remove the cutoff valve and accelerator pump, last fall, but when I take it apart again, I will check again.

Looks like your petcock is very different: has no vacuum port, just a fuel outlet. Suppose the fuel pump pulls enough fuel to the carb without need of vac, but going to gravity feed may create a fuel starvation issue. Have to compare a petcock from each kind to see for sure. 04-07 use the same gravity feed petcock with vac from manifold to a "t", from T to carb air cutoff valve and other side of the T to the petcock. The air cutoff valve and the accelerator pump (on the corner of the float bowl) both use a rubber diaphram. Just check for holes/cracks and seals ok.
Tom

I don't know enough about the petcocks to say one way or another. I do know, there were threads on this and VTXOA about multiple members with 2003 VTX's and removing the fuel pump, going to gravity feed, without changing the petcock with success. I only removed the fuel pump per multiple recomendations on the forums, because of their tendency to fail, and the cost of replacement. I did remove the cutoff valve and accelerator pump, last fall, but when I take it apart again, I will check again.

The 1300 gas cap does not vent. 1800, yepper and I wished I could have used one but they're different. Since I am using a previously rusted tank, the VENT line was closed by rust, I ended up making a vented cap with a drill and progressively larger hole until it vented enough. There's a thin washer (?) on top of the rubber seal in the cap and it's has a little play. I drilled through a small section of the rubber and through that washer . Still seals enough so I don't get any gas leaking and I have a vent. Cost nothing to do vs $1500.00 for a new tank (at todays new tank pricing). Was around 1000.00 when I did this in 2016.

I think I follow what you did, but can you take the cap off and send me a photo? I was begining to wonder if the problem was similiar to this, vapor lock or the like. Did you do it on the front of the cap, where it would be "highest" to prevent any potential leaks?

I did blow compressed air through the vent nipple on the bottom right of the tank, and I could hear plenty of air running through the tank. But who knows. I'm at the point, I'm happy to drill a small 1/16 hole in the cap to vent a little more.



On a side note, I did fill it up with gas yesterday and rode it down the highway, maintaining 80/85 and I didn't have a single problem. I made about a 20 mile trip, about half highway, half back roads. This is with the OEM exhaust. I was going to bring it up to 90/95 and hold it on the way home, but there was a lot of traffic, and if it started acting up, I didn't want to be in a pack of cars. In my mind, I'm wondering if the problem is worse when the tank is say 1/4 or 1/3 vs when it is full. If so, this would lead me to believe it's a fuel delivery issue. We shall see. I hope to be able to take it out today or Saturday and give it a whirl again.

 

[Vinish]

Before you start messing with the gas cap, just ride it until the problem occurs and then open the gas cap lid and see if the problem immediately goes away.

 

[sumdatx]

Thanks for that. I know when I checked the needle Diaphraghm, I made sure to the clip back where it was, when I got it. But who knows if that is correct.



I completely disconnected the fuel pump and the inline filter. When the fuel pump is connected, the line runs from the petcock down under the seat, where the pump is, and then through the pump back up to the carb. I disconnected the electrical to the fuel pump, and "abandoned it in place". I ended up using a long piece of the fuel line from that setup to run from the petcock to the carb. It's a hard rubber (reinforced) line. The only part number I could find on it is 90---140317 08 05. It says its NBR + PVC. I found that typical fuel line kinked when routing from the petcock to the carb.

I realize the fuel strainer is probably a good idea, but I was trying to remove all fuel restrictions to the carb in an effort to figure out why the bike is behaving the way it is.




I don't know enough about the petcocks to say one way or another. I do know, there were threads on this and VTXOA about multiple members with 2003 VTX's and removing the fuel pump, going to gravity feed, without changing the petcock with success. I only removed the fuel pump per multiple recomendations on the forums, because of their tendency to fail, and the cost of replacement. I did remove the cutoff valve and accelerator pump, last fall, but when I take it apart again, I will check again.




I don't know enough about the petcocks to say one way or another. I do know, there were threads on this and VTXOA about multiple members with 2003 VTX's and removing the fuel pump, going to gravity feed, without changing the petcock with success. I only removed the fuel pump per multiple recomendations on the forums, because of their tendency to fail, and the cost of replacement. I did remove the cutoff valve and accelerator pump, last fall, but when I take it apart again, I will check again.




I think I follow what you did, but can you take the cap off and send me a photo? I was begining to wonder if the problem was similiar to this, vapor lock or the like. Did you do it on the front of the cap, where it would be "highest" to prevent any potential leaks?

I did blow compressed air through the vent nipple on the bottom right of the tank, and I could hear plenty of air running through the tank. But who knows. I'm at the point, I'm happy to drill a small 1/16 hole in the cap to vent a little more.



On a side note, I did fill it up with gas yesterday and rode it down the highway, maintaining 80/85 and I didn't have a single problem. I made about a 20 mile trip, about half highway, half back roads. This is with the OEM exhaust. I was going to bring it up to 90/95 and hold it on the way home, but there was a lot of traffic, and if it started acting up, I didn't want to be in a pack of cars. In my mind, I'm wondering if the problem is worse when the tank is say 1/4 or 1/3 vs when it is full. If so, this would lead me to believe it's a fuel delivery issue. We shall see. I hope to be able to take it out today or Saturday and give it a whirl again.

Yea, I checked a few of those threads too. Everybody seemed to do it your way without issue. You have a good tank and a good vent -- rule that out. LED light inside the diaphram and no holes/creases -- rule that out. At least it runs well up to 85. BTW, the Ignition Control Module cuts out at 130mph. I don't remember mine ever seeing 100
That Seafoam will make one run like crap till it's gone/diluted with fresh fuel. Possible some crud got cleaned lose and needs to work itself through. I've been using the Gumout all-in-one total system cleaner and ethanol treatment. Runs good even when it's in the tank.
I'm out of ideas and have scratched a bald spot on the back of my head -- oh, that was already getting there. Hope you have a solid weekend and better luck finding a cure. Virus maybe
tom

 

[SharpAndCunning]

Before you start messing with the gas cap, just ride it until the problem occurs and then open the gas cap lid and see if the problem immediately goes away.

I thought about this, but trying to unlock the gas cap at 90/95 mph and not dropping it might be a little challenging. Much easier to drill the small hole in the correct location.

Yea, I checked a few of those threads too. Everybody seemed to do it your way without issue. You have a good tank and a good vent -- rule that out. LED light inside the diaphram and no holes/creases -- rule that out. At least it runs well up to 85. BTW, the Ignition Control Module cuts out at 130mph. I don't remember mine ever seeing 100
That Seafoam will make one run like crap till it's gone/diluted with fresh fuel. Possible some crud got cleaned lose and needs to work itself through. I've been using the Gumout all-in-one total system cleaner and ethanol treatment. Runs good even when it's in the tank.
I'm out of ideas and have scratched a bald spot on the back of my head -- oh, that was already getting there. Hope you have a solid weekend and better luck finding a cure. Virus maybe
tom

Agreed. I will blow out the vent in the tank again with compressed air just for good measure. I don't intent on this bike seeing 100mph very frequently. It was doing this at 80/85 with the Hard Krome exhaust, and in Massachusetts, I need to be able to cruise at 80/85 on the highway comfortably, without worrying it it's going to bog down and die.

 

[Vinish]

I thought about this, but trying to unlock the gas cap at 90/95 mph and not dropping it might be a little challenging. Much easier to drill the small hole in the correct location.

Your bike, your decision. I would not think that unlocking the gas cap would be very hard, especially at 95 mph. Bike is very stable at high speed. I think it would be more difficult at low speed. Just put the key in the gas cap slot so it is ready to use when you have the problem.

 

[SharpAndCunning]

Your bike, your decision. I would not think that unlocking the gas cap would be very hard, especially at 95 mph. Bike is very stable at high speed. I think it would be more difficult at low speed. Just put the key in the gas cap slot so it is ready to use when you have the problem.

I meant not dropping the gas cap.But I suppose it's worth a shot.

 

[Vinish]

You do not even have to remove it. Just turning the key to loosen it is enough to break the seal and see if the problem immediately goes away.

 

[SharpAndCunning]

You do not even have to remove it. Just turning the key to loosen it is enough to break the seal and see if the problem immediately goes away.

Removing the gas cap does not make the problem immediately go away.

It got pretty bad at one point, and I pulled over and noticed the bottom of the rubber hose that's the overflow was wet with gas. I'm not sure I understand what this means. Could the carb be flooding? If so, what besides the needle under the float would cause that? I just replaced that in September because the air box was filling with fuel. I checked the float last week, and it seems to move smooth and freely.


When it happens, with the stock pipes, you can actually hear the carb, it's making a loud whooshing sound. Almost like the sound a big old quadrajet makes when you slam open the secondaries. I actually ran out of gas today at one point and had to switch to Reserve, and it felt identical to whats happening when I ride.

But what I don't understand is why, when it happens, if you pull in the clutch, the bike will shut off immediately. Give it three seconds, dump the clutch, or engage the stater, it starts right back up and continues on, until the next "episode".

I'm going to take it back apart. Remove the tank tomorrow, and check everything again.


I'll check the line from the petcock to the carb, I plan on adding fuel to the tank via a gas can, and recording flow at the carb, to make sure it's getting the gas from the tank.


Then I'll check the carb inlet. I'll remove the top cover and inspect the diaphragm again, just for shi*s and giggles.


I did inspect the fuel float last week and it seems to move free and smooth.

The part that doesn't make sense is the wet rubber line. Like it was "overflowing". Could there be a bad coil that stops firing, intermittantly, and the bike goes pig rich? Is there a way to test coils?

It's happened so much, I can almost feel it comming on, the bike starts loosing power, just a little, like you let off the throttle, ever so slightly, even though you didn't, and then, buck buck buck, sputter sputter.

 

[JPT]

Removing the gas cap does not make the problem immediately go away.

It got pretty bad at one point, and I pulled over and noticed the bottom of the rubber hose that's the overflow was wet with gas. I'm not sure I understand what this means. Could the carb be flooding? If so, what besides the needle under the float would cause that? I just replaced that in September because the air box was filling with fuel. I checked the float last week, and it seems to move smooth and freely.

Is this hose the hose under the bike right in front of the rear tire, or is this the hose on the side of the carb.

The hose to the side of the carb I would assume it would be a Carb Flooding issue.

 

[SharpAndCunning]

Is this hose the hose under the bike right in front of the rear tire, or is this the hose on the side of the carb.

The hose to the side of the carb I would assume it would be a Carb Flooding issue.

yes, the hose of the side of the carb, sorry I wasn't more clear.