Fuel starving on throttle up

[biffvc]

Problem: Idles fine, but dies when I twist the throttle.
History: Full carburator cleaning, including ultrasonic cleaning of all jets, replaced all tubes and seals (Thank you Red Eye), and set all adjustments to factory specs.  Added in-line fuel filter (never used one before and it may be the problem.) After rebuild I filled tank w/ fuel, added STA-BIL,  and rode for about an hour.  Ran perfectly. 

Then let it set up about 3 months.  (I know, I know...but stuff happens.) STA-BIL was in it so I felt safe.

Added some Techron (that has worked well for me in the past) cranked it again, and it ran rough for a while, with some backfiring, then smoothed right out.  Drove for about 30 minutes, had a bit of hesitation 1500 to 2000 rpm range but not much, then it seems to hit after-burner and accelerate like crazy. As I was returning home it started acting weird.  It died as I entered garage.  I restarted it without touching the throttle and it started and idled fine, but as soon as I turned the throttle it immediately died. 

I plan on replacing the fuel today and test the fuel line, but that's all I have thought of so far.

I read the other posts on fuel starvation and they don't seem to be the same issue, but they may be.

I've gleaned much from this board over the years but I thing this is my first post.  I appreciate your thoughts and advice.   Thanks....bvc

[The emperor has no clothes]

Many people have had trouble with an added fuel filter. Although your issues don't sound the same. Sounds like clogged slow jets, but you say they were recently cleaned. Might check that your petcock is working properly.

[Beardo]

Up here, we regularly go 3 months of storage without issues with just Stabil or Seafoam in the fuel. Can't see your carbs having issues just because of that.

Check petcock, remove the fuel filter..."easy" stuff first. Often, when problems arise, I look to the last thing I did that might have cause the problem.

[gordonv]

Sounds like definant fuel starvation. Enough fuel to idle, but not enough to accelerate.

I too would do without the filter, but.

How did you add the filter in? Did you just cut the fuel line and add it, or did you measure the distance that the filter takes up, and remove that length of line, so that the fuel line length wasn't changed.

[Pete]

For it to happen that quick with no outside changes it may be a sudden massive vacuum leak.
Or a fuel restriction the just occurred. Like a vacuum diaphram failure of the petcock.
Switch to reserve and see if the problem goes away.

[Lyle Laun]

Vent line on the fuel tank plugged ? Open the fuel tank and then restart it and see if it will rev up

Lyle

[biffvc]

Sounds like definant fuel starvation. Enough fuel to idle, but not enough to accelerate.

I too would do without the filter, but.

How did you add the filter in? Did you just cut the fuel line and add it, or did you measure the distance that the filter takes up, and remove that length of line, so that the fuel line length wasn't changed.

Thanks...I did measure and remove the length of the filter from the fuel line, so it should be the same. I didn't work on it today, so I will try the suggestions all of you have offered (i.e. open fuel cap, valve switched to auxiliary, etc.) before I pull the valve apart.  I did take the fuel rooster apart and check the diaphragm when I rebuilt the carbs, but will check again after the other tests.

You guys a great resource...I really appreciate the help.  I'll post the results after I run the traps.

[biffvc]

For it to happen that quick with no outside changes it may be a sudden massive vacuum leak.
Or a fuel restriction the just occurred. Like a vacuum diaphram failure of the petcock.
Switch to reserve and see if the problem goes away.

I'm going to try this, but I didn't realize that switching to auxiliary would bypass the need for the diaphragm.  It looks like it should control all fuel flow.  I'm definitely going to give it a try.  Thanks 

[gordonv]

The diaphragm works for all or nothing. If it doesn't work in On, then it wont work in Res either.

But there is problems with the dial not being turned enough. You need to FEEL for those clicks as the ball falls into the indents in the Res/Off/On positions. That is why you have the suggestion to do something easy, turn the dial.

You can test the petcock by removing the fuel line from the filter, and place it into a container. Remove the vacuum line for the petcock from the intake, and gently such on it (or use a vacuum pump) to get the fuel to flow when in the On/Res positions. I've never done this, but there should be a good flow. Anything less could be petcock problem. Do with the cap open on the fuel tank.

[Pete]

The diaphragm works for all or nothing. If it doesn't work in On, then it wont work in Res either.

Not true, I had one fail in the last month with 1/2 tank of fuel, by turning to reserve I was able continue riding to a fuel station, filled up and rode 50 miles to home on reserve and repaired the petcock.

If the hole in the diapharm is not to large there may be enough vacuum with addition fuel pressure  by switching to reserve to continue riding.

Another temporary fix is to stop up the petcock drain so that vacuum will act on the on fuel diaphram and the vacuum diapharm to cause it to open.  

[Pete]

Read this thread for info on the petcock

http://www.valkyrieforum.com/bbs/index.php/topic,90839.0.html