Ok, as I keep finding new problems each week with my 84' VF500, I stumble upon this problem. The petcock was not holding any vacuum when I applied the right amount with my hand-held vacuum pump, according to the OEM shop manual. Took it apart to find that the bladder had 2 pinholes in it. Went and ordered a new OEM rebuild kit, installed it, holds vacuum perfectly!! Except when I woke up this morning. I find that my Mint condition tank was sitting in a pool of 14oz of fuel on my work bench Fuel is coming out of the nipple closes to the petcock base. Not the actual vacuum nipple but the one behind it. So, heres my question, is the bladder suppose to be a 1 piece unit or 2 piece rubber bladder? Cause the new one is 2 pieces. The gaskets are sealing nice and tight and are not pinched. Thank you LL
If you look at "12" in the photo from left to right you should have; first metal valve, then nipple/metal cylinder(bridge)/diaphragm, plastic chip to hold spring, metal cap (vacuum). The first metal piece should go between the nipple and diaphragm equal to the metal cylinder(bridge). If the nipple is not through the first metal value then there is no gasket and the gas will leak out. Hopefully this makes sense... I'm horrible and typing what I'm trying to say.
It makes sense now! I just got back inside from the garage, and I'm happy to announce that there's no leaks and the fuel flows! It flows a lot faster in the RES position than ON, but I only have like 2 gallons in the tank. Thank you for the help. Now it looks like I need a new petcock assembly..... The fuel will still flow with the vacuum applied and the fuel in the OFF position. Not very much, but it will still flow. Off to the shop for a whole new fuel shutoff valve. LL
