Petcock and fuel system

[MattA]

I am having problems with my Vision.  Seems two things are wrong, but I can't seem to find anything wrong.

The first deals with the petcock.  I understand what each of the positions does, but what should it actually do.  I have an '83 and when I put it on ON and RESERVE it trickles out both of the two plugs.  When I put it on the PRIME position, it comes out (due to gravity).  Is this how it should work?  I thought that I was able to turn off the flow of any fuel before so I could take the tank off without spilling gas, but now it wont do it.  I have opened up the petcock twice now and have had no success in fixing this "problem."  There is only one way for each part to go back together, so I am clueless on what is wrong.  None of the gaskets are torn or ripped...

The second issue may be because of the above, of seperate.  When I drive for long periods of time (over 10 minutes), my bike will flood itself out.  Usually one cyllander kills and then the other kills a minuite later.  I have to wait for 10 minutes and then it will run again for a little bit of time, but it will flood itself out again.  I am pretty sure it is flooding itself because I can let off on the gas and it will sometimes kick back in.  I checked the floats - they are still free and working, and all hoses are connected correctly.  I think it is the back cyllander that is killing first, because the back carb has much more brown residue on the outside of it, but I am not sure...

Anyway, a response to me either via this site or to MattAtlas@letu.edu would be great.  Thanks!

---Matt

[sgrprincees]

In on and reserve, it should be able to hold its fuel; in prime it should let the fuel flow out.  I have no idea how to fix either of your problems.

[Lucky]

The round rubber gasket behind the handle is worn,  i've had luck fliping it over sometimes, or you can get a rebuild kit, they are on the web Ihhave the address somewhere, or they are on ebay all the time.  i believe there is one or 2 at auction now
--Lucky

[MattA]

So could the leakage of fuel be causing the bike to choke itself out?  The interesting thing is that I believe it has been leaking fuel for some time now, and just now has it been dying because it chokes itself out... before it rode just fine.  Thanks....

---Matt

[Lucky]

well when the bike is off, and the pecock is in "on" or "res", there should be no fuel flow, because there is no vaccume.  next the carb floats should keep the inlet needles closed. both of these (or even one) should keep the bike from flooding when it is off.  if both of these happen to fail while the bike is off, you should see fuel on the ground comming out the rubber overflow on the left side of the carbs.

you haven't mentioned finding gas on the ground, so i'll assume that at least the inlet needles are working.

when the bike dies next time, check for spark, you might have a bad safety relay or rev limiter.

you can disable these systems by cutting both the black./white wire  and the yellow/black wires at the TCI 6 connector plug
--Lucky

[MattA]

I just rode my bike about 35 miles, and it "seemed" to be running ok, but I really didnt do much.  I cleaned out the petcock, sprayed some carb cleaner in the carb, made sure the floats were free, tightened all hoses connecting the carb and air systems, and thats about it.  

No gas on the ground, so I assume the floats are keeping the gas from overflowing.  I have cut the rev limiter wire... That was done close to when I bought the bike.  

If I do not replace the gasket in the petcock, what are side effects other than obviously leakage of fuel.  Will I get worse gas milage?  Will I lose a good vacume in my bike and therefore not be able to suck as much gas out of my tank (although it is difficult to tell, it seems that I am only able to use about 3 gallons of my tank now... I know that if the tank is on "PRIME" it can't really pull from the bottom of the tank due to the placement of the lines, etc).

Anyway, any info is helpful to keep this thing running...

---Matt

[RobTx]

Matt,
The vacuum doesn't suck the gas from the tank, it only opens the petcock in the "on" and "reserve" positions when the engine is running.  The "prime" position lets gas free flow out of the tank, running or not, from the bottom, so it will completely empty the tank except for a little on the right side.  There is a vacuum operated fuel pump that helps pull fuel from the tank.  Don't confuse it with the vacuum operated petcock.  When I have to switch to reserve, my tank takes 3.5 gallons.
Rob

[Rick G]

You need to drain you gas tank , remove the gas tank from the bike  abd then remove the petcock from the tank. Check that the screen tube is not damaged and that  "reserve" tube is intact and in place. Disassenble the petcock and  check that the reserve tube abd  the lower drain are clear.  The item that fails, most commonly  is  the small o ring mounted on the  aluminum stub in the center of the diaphram.  track down a suitable replacement  and  as lucky said turn over  rubber donut with 4 holes  in it . Good luck! ;D

[MattA]

Thanks for the replies...

Rick... I have taken off the petcock, and found that the orangish tube/filter that is connected to the main intake of the petcock... It is fine, no holes and is intact...  Is there another tube also?  When I took it off, there was only a hole for the reserve intake of the petcock.  Is there supposed to be a tube hooked up to this also?  I only know what I have seen, so pardom me for being a bit ignorant... All the passages in the petcock are clear...

I am pretty sure my 4 hole gasket that is located behing the selector knob is not quite bit enough.  Can I add another gasket between it and the selector knob to seal it or do I have to buy a new gasket set ($30)... I have flipped the current gasket with no luck...

---Matt

[RobTx]

Matt,
You also need the o-ring that goes around the selector lever.  You can get one at any hardware store for a few cents.  It's what keeps the lever from leaking.  On top of the lever when it's installed is a wavy washer, and then the plate that holds it on, make sure you have all the pieces.  That should fix any leak.  If the 4 hole rubber piece leaks, it'll just go down the fuel hose, not leak out anywhere if everything else is ok.  As Lucky said, if the needles and seats in the carbs are ok, you won't leak any gas.
Rob

[Rick G]

One more thing, when rebuilding a petcock  I bend the wavy washer slightly, to inclease pressure on the 4 hole washer . From what you describe and  what I read it sounds like  the reserve tube is missing from you petcock. The  it should be sticking out of the  petcock body , inside the filter screen.  in the on position, gas is supplied fron the brass tube the sticks up  a couple of inches , in the reserve position,  gas is supplied all the way to the  bottom of the tank.