fuel petcock valve keeps failing

[fjbiker84]

I own an 84 FJ and several years ago the vacuum valve to the petcock failed - gas flowing out the overflow tubes to the carburetors onto the floor of the garage. OK.  It's the original valve so after 30 years it's got a right to go bad. So I ordered a complete new assembly - 36Y-24500-01-00  - and everything was fine..... until today. After parking the bike in the garage this afternoon a few hours passed and I could smell gas. Didn't take long to fine the problem - same as before.  Is this due to all the alcohol in modern gas?  Is there a different system I could install on my old FJ?  It's my understanding that newer models use a fuel pump instead of this gravity feed type of system.  Any help would be appreciated!

[FJmonkey]

Are you sure its the petcock failing? The normal failure of the 84 to 87 petcock is the vacuum part. This failure prevents fuel flow. Before you start your bike check the oil and make sure fuel did not leak down through into the case.

[Pat Conlon]

Check the lever position on the petcock. You may have it turned to P which stands for Prime.

You do not want to leave your petcock lever in this position.

[FJ1100mjk]

I own an 84 FJ...

Any help would be appreciated!

Here's some help. The o-ring in your petcock, and perhaps its sealing surface is compromised, and causing it to leak. I've rebuilt a few following these procedures that can be adapted to the early FJ petcocks.

Ninja 250 Petcock Rebuild Link

XS650 Petcock Rebuild Link

The XS650 rebuild instructional, addresses the inspection, and if needed, the refurbishing of the o-ring's seating surface in the petcock's body.

I have been using these softer, "ultra-compressible" o-rings, Low Durometer Petcock O-ring that being softer, help with the o-ring sealing on its contact surface.



Additionally, I have been placing a small stainless steel flat washer between the spring and its seat on the aluminum cap (one that the five Phillips/JIS screws hold down), to slightly preload the spring to provide a little more oomph to seal the o-ring. No leaks thus far on my petcocks.   Fingers crossed!

One last thing about the petcock, and not sure if you've done it, but safety wire the petcock's outlet tube to the petcock's body. It could fall out of the petcock, your nice FJ could self-immolate, if not safety-wired in place.

Good luck!

[balky1]

I own an 84 FJ and several years ago the vacuum valve to the petcock failed - gas flowing out the overflow tubes to the carburetors onto the floor of the garage. OK.  It's the original valve so after 30 years it's got a right to go bad. So I ordered a complete new assembly - 36Y-24500-01-00  - and everything was fine..... until today. After parking the bike in the garage this afternoon a few hours passed and I could smell gas. Didn't take long to fine the problem - same as before.  Is this due to all the alcohol in modern gas?  Is there a different system I could install on my old FJ?  It's my understanding that newer models use a fuel pump instead of this gravity feed type of system.  Any help would be appreciated!

I had the same problems on an '85, but you can rebuild it easily. There are rebuild kits available. When you disassemble the petcock, check the diaphragm. It shouldn't be punctured. The O-rings are (unfortunately) expendable goods. You can also stretch the spring a little bit (but don't stretchh it too much).

Ivan

[fjbiker84]

Thanks for the input!  I'll look at trying to rebuild the one on the tank now and use as a back-up.  I went ahead and ordered another complete new assembly.  Could gas leak into the engine?  I'll look at that too.  BTW, I'm wondering if fuel additives like Marine Foam may damage this valve - especially if you put too much in the tank. 

[4everFJ]

http://www.nrp-carbs.co.uk/shop/index.php?route=product/product&product_id=4140

[balky1]

Thanks for the input!  I'll look at trying to rebuild the one on the tank now and use as a back-up.  I went ahead and ordered another complete new assembly.  Could gas leak into the engine?  I'll look at that too.  BTW, I'm wondering if fuel additives like Marine Foam may damage this valve - especially if you put too much in the tank. 

Don't know for the aditives, but gasoline can get into crankcase if your fuel petcock and floats aren't shutting it off. If you noticed fuel leak, check your oil level. If your oil level is higher than it was, by all means, DON'T CRANK THE ENGINE. You can end up with bent rods. You can check if there is too much fuel in one or more cylinder/s by cranking the engine by hand. If it turns without problems, it is probably all well. I personally remove all the spark plugs (after oil change and fixing the leakage) and crank it on battery to expell extra fuel (if there is any).

[red]

FJbiker,

Not sure about the additives, but the ethanol/gasoline can cause a gas tank to rust inside.  Rust particles that get into the petcock can keep it from sealing as it should, even if the petcock is good otherwise.  The good fixes for rust in a tank can be found here, if needed.  Try "fishing" in the tank with a magnet on a stick, and see if you can pull up any loose rust, which would mean you have a rust problem.  For now, you can stick a few small button magnets to the inside of the tank around the petcock, to catch even the microscopic rust before it causes trouble.   I recommend using the new "super-magnets" (neodymium) rather than the old weaker magnets.  Home-improvement stores usually have the good ones for sale.   HTH.

Cheers,
Red

[fjbiker84]

Thanks for comments.  I cleaned the tank as well as possible before installing the new petcock assembly.  Also checked to make sure no gas made its way into the engine.  The tank does have discolored red spots visible on the inside but it's not what I would call corrosion of the metal.  I took apart the vacuum valve mechanism on the petcock that I removed and don't see anything wrong with it.  All the rubber seals are intact and in good condition and the fuel passageways inside the petcock are clear.  The screen on top of the petcock is clean and shows no evidence of debris.  Oh well.  She's back on the road!

[FJmonkey]

Cool, that means you make the next SoCal ride. Not sure when yet but stay tuned in.