What position should the petcock swicth be in for oof

Fuel petcock position depends entirely on what you're doing with your bike at the time.

In normal use, the fuel petcock should be set to the "on" position and left there. In that position, gasoline will be drawn from the tank only when the engine is running and generating vacuum. This prevents overfilling the carbs when the bike sits.

When you're riding the bike and it starts to sputter, it's time to move the petcock to the "reserve" position so that you can use the last few drops in the tank (on a 650 special, this was either .3 or .5 gallons--can't remember which off the top of my head) to nurse your bike to a gas station. Once you've filled the tank, move the petcock back to "on." The bike will still run fine if you keep the petcock in the reserve position, but when it starts to run low on gas--well, you won't have that emergency reserve to get yourself to the gas station.

If you've managed to run the bike out of gas completely, or if you are getting the bike ready for service after having drained the carbs for the winter, you'll need to move the petcock to the "prime" position for a few minutes. This by-passes the vacuum line cutoff mechanism and lets gasoline flow until the carb floats shut off the fuel valve (this is also how all older motorcycle fuel petcocks operated). A sticky float or poorly sealing float valve in the carb can, however, cause far too much gasoline to drain into the carbs (and into the crankcase, if you're particularly unlucky), which is why you should not leave the petcock in the prime position for an extended period of time.

Some Yamaha XS650 motorcycles (can't tell if that's the model you have) have a tank with two fuel petcocks, one on each side, to fuel each carb. If you have a tank with this setup, be aware that setting one fuel petcock to "prime" will affect both cylinders, as there's a crossover tube to equalize fuel levels between the carbs. Also, for reasons I could never figure out, on one XS650 I owned, moving either petcock to "prime" permitted fuel to flow on a gravity feed out of both petcocks simultaneously. I could never figure out exactly why it was doing that.

It sounds like you have an aftermarket petcock on the bike. I am not familiar with a Harley petcock that has a round knob but then maybe just the knob is an add-on. In 1996, Harley went to a vacuum operated petcock, one that gives lots of problems. I cannot tell you which way is reserve on your petcock. The only way to tell for sure is to pull the petcock out. You'll see a plastic strainer on top of the petcock. Inside the strainer, there is a tube that runs approximately half way up the strainer. Select a position on the petcock valve and blow through the petcock. When you feel the air come out of this tube, this is the "ON" postilion. Right beside this tube inside the strainer is another hole directly into the petcock. Find the position that allows for air to pass through this hole and you've found the "reserve" position. The remaining position should be "off".

Good Luck
Steve

You have a vacuum operated petcock....so that when engine starts and draws vacuum...a diaphragm lifts in the petcock to supply fuel to carb. When the engine shuts off...vacuum is lost and the petcock closes.
If you run the tank empty....in order to get fuel into the carb and get the bike started initially....you can open the petcock without engine vacuum by rotating petcock to the PRIME position. Once started return the petcock to the ON position. If you leave it on prime....with engine off...fuel may leak into carb and run into engine and contaminate crankcase oil with fuel.

Either the intake tube on your fuel petcock has fallen off, Your petcock has worn out and is allowing fuel from the reserve position to leak into the on position hole , or you had the lever in the wrong position. If you had the petcock turned to the correct positions, the you may want to drain the tank and remove the pet **** for inspection. If the fuel inlet tube for the ON position has fallen off, you in effect, have no reserve. If the petcock is worn out you will need to replace it so it will work the way it is supposed to.

problem is probably the fuel petcock try this test disconnect the fuel line and get a good length of clear line enough to reach a container hook it up to the petcock and turn the petcock in the on position and observe the flow of fuel to see if it is flowing freely try this in the on and the reserve position.
if it id restricted remove the petcock and clean the obstruction of rebuild or replace it.

Do you have a petcock on the bottom of the gas tank? If so, if you have a "reserve" the petcock will have three positions, off, regular and reserve. If you only have a two position petcock you have no reserve function. Petcocks work by taking the gas in the petcock tube higher up in the gas level, once the gas level drop below a certain level on the gas tank pickup tube, the petcock has to be switched to reserve where the tube picks up gas at a lower level. Hope this is not too confusing.

E 210882 Motherboard power swicth, rest swicth, HDD led, - P led and positive P led pins

You're bike may be equipped with a vacuum operated petcock. See if the fuel valve has a "prime" position on it. If so, put it in this position. If you still don't get any fuel to the carb, you'll have to remove the petcock from the tank and clean the screen or unstop the petcock. I'd put a manual petcock in and block the vacuum line.

If you already have a manual petcock and you're not getting fuel, remove the petcock, clean the screen, and blow air through the petcock in both the "On" postition and the "Res" position.

there is not a off position i have a 1999 GSF bandit 1200 which i had the same air box gas problem. the positions are On, Reserve, and Pri. if its leaking back into the air box the petcock is not working correctly pull the tank off or disconnect the gas line and vacume line fuel should not leak out if it does the diaphram is riped replace the petcock. Also if you airfilter got soaked it needs to be replaced