Fuel petcock leaking where can i get a rebuild kit on 2001 750 katana diaphram bad

They do make rebuild kits for petcocks. Just going to depend on if they make one for your motorcycle or not. I did do a quick search for Harley petcock rebuild kits and they do make them.

if your bike has a vacuum operated fuel petcock on the tank....ensure that it is set in the ON position and not prime PRI position. Often as these age, the diaphram leaks and raw fuel leaks into the vacuum line, into the engine and then crankcase.
You could test by removing the vacuum hose, switching briefly to prime and see if fuel starts leaking out the open vacuum port on the petcock. There are kits to rebuild the petcock...and definitely change your oil and filter to get the contamination out.

Your model 95 or 96 VF750 Magna does not have a fuel pump. I believe the part you are talking about is the vacuum fuel petcock assembly. The part is only sold from Honda as an assembly.The part number is # 16970-MZ5-003 and runs about $120.

Some Viragos used a vacuum operated fuel petcock that allowed the fuel supply to open when the bike started and shut off when it stopped. There was a vacuum line from the intake to the petcock and this vacuum acted on a diaphram to open the fuel.
Sometimes the diaphram leaks and the intake vacuum pulls in fuel....causing a very rich mixture.
If you find it has a vacuum operated petcock, you could remove vacuum line and briefly open the
petcock manually using the PRI for prime position to see if fuel leaks out the vacuum port.
There are rebuild kits for the vacuum operated petcock

First check to see if the oil level in your crankcase is too high. If you have a vacuum petcock malfunction (hole in the diaphragm) or if the fuel petcock is left in the prime position and a float needle sticks, then you get you get gas running into the cylinders, past the rings, and into the oil.
When you start your motorcycle the oil/gas mixture has no place to go, the crankcase is too full, and the mixture exits through the crankcase breather into the air box where it will ruin a paper air filter. Always turn your fuel petcocks off when not driving. If the petcock diaphragms are bad rebuild the petcock with K&L rebuild kits or replace the fuel petcocks with new ones. If the float needles in the carburetors are bad or sticking, take the carburetors apart, clean them, and replace any worn or damaged parts You will have to change your gasoline saturated oil for it will no longer properly lubricate your motor.Just a note: in 1983 brand new Honda's would fill there engines in gas. All the components were clean and new. This can happen to any machine in any condition at any time. When not riding always turn off the fuel vales never leave them in the prime position.

Either the vacuum operated petcock is stuck in the flow position as well as a float needle is stuck in the open position. Two things would have to be wrong so that the fuel would over flow the carburetors and run past the piston rings into the crankcase. Or, more likely, the vacuum diaphragm inside the fuel petcock is leaking and the fuel is flowing down the vacuum line into the engine. I would start by inspecting the vacuum fuel petcock. If you unplug the vacuum line and gas is dripping from the vacuum line then you will need to rebuild or replace the fuel petcock.

Sorry unless honda does a rebuild kit, your out of luck.
The leak is often in the diaphram, and will be unique for that petcock, although a number of models may use the same petcock.

did you try the fuel petcock on the bottom of the tank? If not, pull it out and check the fuel filter on the top of it. If it won't start because of no fuel, that maybe the problem or it could just be a vaccum leak. Check the tubes for leaks or just replace them, they are cheap. If it isn't starting because it floods out from to much fuel, then it might just need a new petcock. How did the diaphrams on the top end of the carb look?

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

You will need a new petcock. The internal seals are gone.