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  Topic Review (Newest First)
09-26-2019 01:04 PM
SharpAndCunning
Quote:
Originally Posted by Donnie Downer View Post
Don’t know.
But I DO know the vacuum petcock doesn’t help “suck” fuel. The vac just opens a plug. It’s a safety thing. That's it.

I have been running a vacuum-less petcock on mine for 10 yrs. no issue.

Have you pulled the petcock to check the screen, checked the diaphragm with a bright light behind it?

Could also be non fuel related, corroded common electrical ground at front coil can cause the bike to cut out.
What year is your bike? Is it a 2003? Did you remove the fuel pump? I have checked the screen in the petcock, I even replaced it (I crushed the one that was there getting it out).

The diaphragm on the carb top? YUP! I've taken it out 2X and check it. Once in the pure darkness with a flashlight. No cracks or splits. It's still soft and pliable.

I'll check the electrical connector on the front coil, thanks! I would think If that was the problem, it would cut out in other gears too, but I'm happy to check. Thanks!
09-26-2019 05:46 AM
Donnie Downer
Quote:
Originally Posted by SharpAndCunning View Post
Quote:
Originally Posted by Donnie Downer View Post
It doesn’t
Then why does my bike run out of fuel in 5th at WOT without the fuel pump?
Don’t know.
But I DO know the vacuum petcock doesn’t help “suck” fuel. The vac just opens a plug. It’s a safety thing. That's it.

I have been running a vacuum-less petcock on mine for 10 yrs. no issue.

Have you pulled the petcock to check the screen, checked the diaphragm with a bright light behind it?

Could also be non fuel related, corroded common electrical ground at front coil can cause the bike to cut out.
09-25-2019 11:36 PM
SharpAndCunning
Quote:
Originally Posted by Donnie Downer View Post
It doesn’t
Then why does my bike run out of fuel in 5th at WOT without the fuel pump?
09-25-2019 01:13 PM
Donnie Downer
Quote:
Originally Posted by SharpAndCunning View Post
Maybe the vacuum line to the petcock helps "suck" the fuel through the hose under high load engine situations and prevents the carb bowl from running dry.
It doesn’t
09-25-2019 12:58 PM
SharpAndCunning Just wanted to bump this thread.

I'm starting to wonder if I either need to re-connect the fuel pump, OR get a vacuum actuated petcock. Maybe the vacuum line to the petcock helps "suck" the fuel through the hose under high load engine situations and prevents the carb bowl from running dry.

But $100 for a petcock, or $100 for a new fuel pump, I mean it's kind of a what do I do situation.
09-19-2019 10:24 PM
SharpAndCunning
Quote:
Originally Posted by Hans&Feet View Post
Unscrew bowl drain screw.
You are using the manual petcock, check fuel flow from carb bowl.

Usually when the Main tank fuel runs out I get a lean out pop.
If I pay attention I can hear the difference as it starts running lean.

About 3 weeks ago I forgot that I changed to trip B. I felt it running rougher and gave it throttle.
Squirt from accelerator pump was good for a few milliseconds but loud fat backfire from dry main jet.

105/110 MPH, VTX speedo or GPS. GPS than that is about it... Out of HP

Unscrew drain screw and what? Check for debris?


As I noted above, I did check fuel flow from the tank. Same strong steady flow "ON" or "RES".

That's 105/110 indicated on speedo. I don't think it's the speed. It's the 6/7 Seconds in 5th gear at WOT that's causing the problem. No other gear can I hold it open that long. But in 5th, I can start at 70mph and romp on it, and hold it there. It's like I'm sucking the fuel bowl dry. I don't trust the bike to ride very far, like commute to work, etc. (I don't want to have a problem and be late to work).

This weekend, I'll take it out and ride it around normally, get on it, etc. I don't expect the bike to be a race bike, and I know 6/7 Seconds at WOT in 5th really isn't what this bike is designed to do. My fear, is this is a symptom of a problem that might get worse, and i'd rather fix it now.
09-19-2019 08:44 PM
Hans&Feet Unscrew bowl drain screw.
You are using the manual petcock, check fuel flow from carb bowl.

Usually when the Main tank fuel runs out I get a lean out pop.
If I pay attention I can hear the difference as it starts running lean.

About 3 weeks ago I forgot that I changed to trip B. I felt it running rougher and gave it throttle.
Squirt from accelerator pump was good for a few milliseconds but loud fat backfire from dry main jet.

105/110 MPH, VTX speedo or GPS. GPS than that is about it... Out of HP
09-19-2019 05:31 PM
SharpAndCunning
Quote:
Originally Posted by Hans&Feet View Post
>>>> Provide links>>>There seem to be quite a few threads from back in the day about this happening. Bikes bucking, sputtering, or dying out at WOT Was there ever a mainstream fix?


What about the strainer in the carb hose fitting??
2003 parts fiche shows it..
30 SCREEN, FUEL STRAINER 16176-MW3-A80

https://www.partzilla.com/product/ho...1a558e76d3ae06
Here's two threads:

https://www.vtxoa.com/forums/7-vtx-1...-o-t-post.html


https://www.vtxoa.com/forums/7-vtx-1...e-2.html?amp=1

My 2003 didn't have that fuel strainer. I looked very carefully when I first took the carb out. I haven't put another one in. The parts fishe show it, but the 2003 had an inline filter under the seat before the fuel pump too, I don't know if they were actually there.
09-19-2019 12:38 PM
Hans&Feet >>>> Provide links>>>There seem to be quite a few threads from back in the day about this happening. Bikes bucking, sputtering, or dying out at WOT Was there ever a mainstream fix?


What about the strainer in the carb hose fitting??
2003 parts fiche shows it..
30 SCREEN, FUEL STRAINER 16176-MW3-A80

https://www.partzilla.com/product/ho...1a558e76d3ae06
09-19-2019 12:13 PM
SharpAndCunning
Quote:
Originally Posted by gmarshall View Post
Replace the gas tank petcock. There is a screen inside and when I removed mine it was corroded and falling apart. With the new petcock the motor has more pep. That was my fix.

G

So I took the line off the petcock last night and put another line onto it, into a bucket, the flow is fine. There is no discernible difference between the flow rate from RES vs ON.

When the fuel level gets lowers, approx 1.4/1.5 gallons, sure, it flows a little slower, but it's still a solid stream.

So I think I've ruled out the petcock screen as far as a culprit. I don't have a big enough Metric open end wrench to get it out (my set stops at 20mm) so I also put a mechanic scope into the drained tank and looked, and the filter is white, and there is no sign of rust/heavy corrosion.

Obviously the scope can't pick up on debris, but the flow rate shows there's not a big clog.

I can't honestly say if this was happening when I had the fuel pump attached or not, it only happens when I run WOT in 5th. I'm guessing it didn't, but if the 2004+ bikes didn't have a fuel pump, there has to be a fuel delivery issue here. But the line runs direct from the petcock, across the top of the engine, right to the carb. It's not pinched or restricted anywhere.


There seem to be quite a few threads from back in the day about this happening. Bikes bucking, sputtering, or dying out at WOT Was there ever a mainstream fix?
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