Fuel starvation at highway speeds.

[Fray Bentos]

After riding at highway speeds for around a mile my bike starts to act as if it is running out of fuel. If I slow down to 50-60 for a short spell, it's good again for about another mile.

It does not do this at lower speeds with short bursts of wide-open throttle. I seem to have to be doing 70+ for a stretch to get this to happen, and it does not always do it either just to frustrate things.

I'm guessing that the bowls are emptying quicker than they can refill under that demand.

I am not the original owner although this is a new problem. I have had this bike for 4 years.
A couple of years back I changed the OEM Petcock for a new OEM petcock, cleaned out the tank, run some B12 through, changed all the small vacuum hoses to and from the carbs, and removed a set of straight-through 6 into 6 pipes. Outside of routine maintenance I have not tampered with anything else.

I am still using it. Because I hardly ever use the highways it's not causing me any unavoidable drama, but obviously still needs resolving.

No change with the gas cap open
The vent line is not pinched or restricted and has an open T . It's quite a long line though if that matters. It hangs right down underneath the bike.
No change if the petcock is on reserve
The Petcock appears to flow freely under suction.
Air filter and box intact and clean. It's a K&N filter. (4 years old)
The Fuel line is not OEM, It's a steel braided line. But why fail on me now? Anyway, I'll change that when the new OEM gets here in a week or so.
I guess I should pull the petcock and check the in-tank filter sleeve.
Re-check all the vacuum lines.

If I assume that I am on the right track with fuel supply, I can't think of much else that would limit flow before we get to the carb rail, or the carbs themselves.

I'd be really grateful for any additional similarly simple checks you can recommend I undertake in the first instance.

Or just tell me if I am a million miles off course and Y'all have heard this problem a thousand times already.

[Jersey]

I had this happen, but only when running over 90+ for a while.  I replaced my Dan Marc cutoff with the larger orifice and did the mod to the OEM petcock to eliminate the vacuum line.  For me it only happened when the tank was less than 1/2 full.  So figured it was related to the vacuum not being strong enough at the higher rpms to open the valve.  Haven't had an issue since doing this.  I hope that helps.

Jersey

[Skinhead]

I'd look for a kinked or clogged tank vent line.  If you have an extra key, put it in the filler cap and go for a ride.  If the fuel starvation occurs, open the cap.  If the problem corrects itself when you open the tank, the vent is probably not working.

The other issue could be a perforated diaphragm in the petcock, this could be checked by applying a vacuum to the vac line on the petcock, if the vacuum doesn't hold, replace the cover set.

[RonW]

The other issue could be a perforated diaphragm

this .....

The vent line is not pinched or restricted and has an open T . It's quite a long line though if that matters.

• It hangs right down underneath the bike.

The vent line terminates at the kickstand bracket.

[Foozle]

After riding at highway speeds for around a mile my bike starts to act as if it is running out of fuel. If I slow down to 50-60 for a short spell, it's good again for about another mile.

It does not do this at lower speeds with short bursts of wide-open throttle. I seem to have to be doing 70+ for a stretch to get this to happen, and it does not always do it either just to frustrate things.

I'm guessing that the bowls are emptying quicker than they can refill under that demand.

I am not the original owner although this is a new problem. I have had this bike for 4 years.
A couple of years back I changed the OEM Petcock for a new OEM petcock, cleaned out the tank, run some B12 through, changed all the small vacuum hoses to and from the carbs, and removed a set of straight-through 6 into 6 pipes. Outside of routine maintenance I have not tampered with anything else.

I am still using it. Because I hardly ever use the highways it's not causing me any unavoidable drama, but obviously still needs resolving.

No change with the gas cap open
The vent line is not pinched or restricted and has an open T . It's quite a long line though if that matters. It hangs right down underneath the bike.
No change if the petcock is on reserve
The Petcock appears to flow freely under suction.
Air filter and box intact and clean. It's a K&N filter. (4 years old)
The Fuel line is not OEM, It's a steel braided line. But why fail on me now? Anyway, I'll change that when the new OEM gets here in a week or so.
I guess I should pull the petcock and check the in-tank filter sleeve.
Re-check all the vacuum lines.

If I assume that I am on the right track with fuel supply, I can't think of much else that would limit flow before we get to the carb rail, or the carbs themselves.

I'd be really grateful for any additional similarly simple checks you can recommend I undertake in the first instance.

Or just tell me if I am a million miles off course and Y'all have heard this problem a thousand times already.

I think you're exactly on the right track.

Recheck the vent line to make sure it's not kinked or otherwise obstructed.  Length shouldn't matter - as mentioned, it should hang down and exit near the side stand.  The "T" connecting the two sections in the middle will be open (as yours is).

It could be a clogged filter - but if you replaced the petcock with a new OEM, I wouldn't think this would be the case.

Personally, I've never run across a braided steel fuel line on a Valkyrie.  As you said, it's curious why this would suddenly matter now.  Still, you may find your problems corrected with installation of a new OEM gas line.

Please let us know how it all turns out.

Terry

[JimC]

If you do not have an electric shut off valve, I would check the fuel lines. If you do not know the origin of the braided fuel line, look there.
Back when the braided lines became popular, there were a lot of cheap (Chinese) companies making them, and they were doing so with the cheapest fuel lines available because you could not actually see the lines, you could not tell.
With today's gasoline you need high quality lines or they get soft and collapse under high demand.

Jim

[Chrisj CMA]

Just because you put a new petcock on there a couple years ago doesn’t rule out it’s a bad petcock now. The symptoms you describe = bad petcock. If so it will get worse and worse until you fix or replace. I fixed mine once but when it happened again I went with a Pingel and never looked back.

[Bagger John - #3785]

I had a similar situation happen with my '99 CA-model Tourer on the way home from work several years ago. Backroads speeds were fine but the bike almost died at anything over 50MPH, so I found the nearest exit and bailed then took a leisurely cruise through suburbia to get home.

The cause - as pointed out above - was a pinholed diaphragm.

The petcock which replaced the bad one failed spectacularly  (as in, no flow whatsoever) on a run a couple years later. I ended up putting a snubber/restrictor in the vacuum line and while this seems to have addressed the issue I'm going to convert to a non-vacuum type with electric shutoff - as many others have done.

[Fray Bentos]

Thanks, I will check all the mentioned as soon as I get chance.

Just poking around with a torch following lines. After the fuel line T at the carbs, is it normal that the lines from the T go under the vacuum line that goes to the airbox from the pair valve? It clearly causes a dip. Should this not be above?

[Bagger John - #3785]

Thanks, I will check all the mentioned as soon as I get chance.

Just poking around with a torch following lines. After the fuel line T at the carbs, is it normal that the lines from the T go under the vacuum line that goes to the airbox from the pair valve? It clearly causes a dip. Should this not be above?

Any dip = potential air bubble. This may be your problem.

[gordonv]

Thanks, I will check all the mentioned as soon as I get chance.

Just poking around with a torch following lines. After the fuel line T at the carbs, is it normal that the lines from the T go under the vacuum line that goes to the airbox from the pair valve? It clearly causes a dip. Should this not be above?

You might like to add your location to your profile, so we don't think you are looking around your bike for a fuel problem with an open flame.

Vent line was the first thought, but you've run it with an open filler cap.

I would think that non OEM fuel line.

Jeff had a good point on the verifying of the petcock, that it's working right.

[Fray Bentos]

You might like to add your location to your profile, so we don't think you are looking around your bike for a fuel problem with an open flame.

Oh yes, sorry I mean a flashlight. Don't want you thinking I am captain caveman, although it wouldn't be wildly uncharacteristic.

Doesn't appear to be any way to replace the fuel line and re-route the airbox line without removing the airbox. That is something to look forward to.

[Foozle]

Thanks, I will check all the mentioned as soon as I get chance.

Just poking around with a torch following lines. After the fuel line T at the carbs, is it normal that the lines from the T go under the vacuum line that goes to the airbox from the pair valve? It clearly causes a dip. Should this not be above?

It looks like that's normal (see below URLs).

If things worked well before, look for something that's either changed or has that potential.  Jeff and Ron's suggestion of a pinhole in the petcock diaphragm is a good one.  Plus, it's relatively easy to check and straightforward to remedy.

Personally, I've had good luck with the OEM petcock, but I've trained myself to shut off the fuel whenever the bike isn't running.  Many others have gone to a Pingel with good results.

Terry

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[Twofeather]

I had the same thing happen to me yesterday. As long as I didn't go over 45 mph the bike would run fine, if I went over 45 mph it would act like it was running out of gas. I had just filled up so I knew that wasn't the problem. I checked the vent hose it was clear. I checked the vacuum hoses all looked good. We were about 75 miles from home and I didn't have anyone to call, so I took it all apart on the side of the road. I found that the screen on the petcock was covered up with a bunch of junk that must have been in the gas tank. I cleaned off fuel filter/screen then I dumped A little bit of gas out the petcock hole to try I get anymore junk out. Put it all back together and it ran like a champ all the way home. I had read this post last Friday but had not experience this problem before. Now I have. Hope this helps. Ride safe

[RonW]

I had the same thing happen to me yesterday.

 ..... so I took it all apart on the side of the road. I found that the screen on the petcock was covered up with a bunch of junk that must have been in the gas tank. I cleaned off fuel filter/screen .....

Do you mean Screen 4?

And you took it apart on the side of the road? Amazing.

[Twofeather]

RonW, yes

[Jruby38]

Ditch the OEM POS fuel valve for a manual Pingle. You will not out run it. 85-90 mph on interstate mile after mile.

[The emperor has no clothes]

Ditch the OEM POS fuel valve for a manual Pingle. You will not out run it. 85-90 mph on interstate mile after mile.

I’ve run 100 mph, 2up, pulling a loaded trailer. With an “OEM POS fuel valve” mile after mile. 

[Jruby38]

The only thing worse than the fuel valve is the cheep wrinkle plastic chrome

[Avanti]

Ditch the OEM POS fuel valve for a manual Pingle. You will not out run it. 85-90 mph on interstate mile after mile.

I’ve run 100 mph, 2up, pulling a loaded trailer. With an “OEM POS fuel valve” mile after mile. 

Do you happen to know the ambient temperature at the time? Just wondering if a vapor lock is possible. I lost fuel to my right carburetor bank, all three bowls went dry at about 10 miles into a 6-7% grade uphill run two up pulling a trailer in 80 to 85 degree temperatures.

[The emperor has no clothes]

Ditch the OEM POS fuel valve for a manual Pingle. You will not out run it. 85-90 mph on interstate mile after mile.

I’ve run 100 mph, 2up, pulling a loaded trailer. With an “OEM POS fuel valve” mile after mile. 

Do you happen to know the ambient temperature at the time? Just wondering if a vapor lock is possible. I lost fuel to my right carburetor bank, all three bowls went dry at about 10 miles into a 6-7% grade uphill run two up pulling a trailer in 80 to 85 degree temperatures.

It was probably only 80* at that trip. But I’ve run it at 95-100 mph in temps above 100* before. (1up and no trailer)

[Avanti]

There must be an equation for this.

Load ÷ Ambient Temperature + Posted Speed = Cooling Efficiency

[The emperor has no clothes]

There must be an equation for this.

Load ÷ Ambient Temperature + Posted Speed = Cooling Efficiency

I’m sure there is. But I do know both of my Valkyries perform well in extreme heat of even 128*. The only times my fans come on is if stopped in traffic or going very slow up a grade.

[Valkorado]

Ditch the OEM POS fuel valve for a manual Pingle. You will not out run it. 85-90 mph on interstate mile after mile.

I’ve run 100 mph, 2up, pulling a loaded trailer. With an “OEM POS fuel valve” mile after mile. 

Do you happen to know the ambient temperature at the time? Just wondering if a vapor lock is possible. I lost fuel to my right carburetor bank, all three bowls went dry at about 10 miles into a 6-7% grade uphill run two up pulling a trailer in 80 to 85 degree temperatures.

Curious if you had a Dan-Marc installed when this occurred?

[Fray Bentos]

 

Sorry for the delay in reply it took a while for a parts delivery to arrive.

I didn't check each item individually to narrow it down I simply did the below whilst I was in there and now it works just like it used to. I actually think it starts up quicker now.

Vent Tube was fine. Re-routed correctly, as shown above.

Tested Petcock with Mityvac, holds pressure, flows well. No failure there. OEM.

Pulled the petcock and tank screen, This was clean and clear.

Threw out the K&N and installed an OEM filter because of comments in the forum.

Pulled the Airbox and its tentacles. The tentacles were clamped on with stainless jubilee clips, so switched those six out with OEM black clamps being careful to align the hoses as they were not aligned in their groves and get them seated properly (That was fun!)

I am not entirely sure if it was my doing or not but vacuum hose No.12 (Back right of airbox) had slipped off before I had started to remove the airbox. Possibly the cause all along?

Pulled off the braided fuel line - Very brittle, so brittle I broke the end off and it was very badly cracked the entire length once I pulled the braiding off.  8mm internal and 2 inches longer than the OEM - Replaced with OEM. OEM is much stiffer rubber.

Checked all vacuum lines the best I could. Changed the petcock vac line with new.

A big thank you to you all.

[Jims99]

Glad you got her back to normal. Thanks for the update 

[Foozle]

 

Sorry for the delay in reply it took a while for a parts delivery to arrive.

I didn't check each item individually to narrow it down I simply did the below whilst I was in there and now it works just like it used to. I actually think it starts up quicker now.

Vent Tube was fine. Re-routed correctly, as shown above.

Tested Petcock with Mityvac, holds pressure, flows well. No failure there. OEM.

Pulled the petcock and tank screen, This was clean and clear.

Threw out the K&N and installed an OEM filter because of comments in the forum.

Pulled the Airbox and its tentacles. The tentacles were clamped on with stainless jubilee clips, so switched those six out with OEM black clamps being careful to align the hoses as they were not aligned in their groves and get them seated properly (That was fun!)

I am not entirely sure if it was my doing or not but vacuum hose No.12 (Back right of airbox) had slipped off before I had started to remove the airbox. Possibly the cause all along?

Pulled off the braided fuel line - Very brittle, so brittle I broke the end off and it was very badly cracked the entire length once I pulled the braiding off.  8mm internal and 2 inches longer than the OEM - Replaced with OEM. OEM is much stiffer rubber.

Checked all vacuum lines the best I could. Changed the petcock vac line with new.

A big thank you to you all.

Agreed - thanks for following up with this.  It's how we all learn to maintain a bike that most dealerships aren't able (or willing) to competently deal with.

I've found the Valkyrie to be a bit persnickety when it comes to the fuel line.  In some circumstances, just a little added length or slight bend seems to make a big difference.

Glad you got it all straightened out.

Ride safe!

Terry