Another leaky petcock...gas cap this time?

I have the same leaky petcock issue...gas all over the floor. Mine is from the petcock, though. I pulled the tank, disconnected all lines, and it leaks probably an ounce every 3 minutes. I have taken apart the petcock, and everything looks fine. Still leaks. Put a little stronger spring in, still leaks. Now when I listen to the tank as it sits (and drains gas on the floor), I can hear the hissing of air....and it is coming from the gas cap. Is the gas cap supposed to leak, or to seal completely? I am looking at the rubber seal of the gas cap right now, and it is probably the original seal....cracking a bit, and hard as a rock. Is this the problem? Could it be?

 

No, that shouldnt be the problem. My gas cap was pretty bad, got stolen before and the theifs pryed up the gas cap to fill her up. While I have fixed most of the problem it still leaks a little gas if i fill her up to the brim. I dont have a petcock issue, I will also go and take off the lines and open my gas cap to see if there is any change... Have you tried replacing all of the gaskets/o-rings on it?

Edit: There is a thread right below this one that might help you: Petcock Issue

 

Just because everything looks fine, doesn't mean it is.

I swapped my vacuum diaphragm a while back, it leaked. It put in a stronger spring, it leaked.

Then I chatted with Chacal.

Turns out that, near as we can figure, the back of the selector lever was warped and needed to be sanded down flat. I also replaced the o-ring and wave washer, and put some silicone grease on the o-ring when installing. Also check the rubber bit with the five holes in it behind the selector lever; see whether it's sitting on the two mounting pegs properly, or if it's torn/flattened.

Hasn't leaked a drop since.

 

According to the parts guys at my local Yamaha store this is the #1 cause of fuel valve issues. That disc seals the whole system.

That solved my problem.

 

Is that the same on my XJ700? I am thinking, and coming up blank on that part of the petcock....

 

Cheby, yes it's the same "concept" (all yammy petcocks are designed the same) but the 700 uses a different sized disc than the other models:

fp12) Petcock fuel position Selector Lever Distribution Valve. This is the hard plastic molded disc with the 4 holes in it that fits below the selector lever. These are usually worn out and need to be replaced whenever you go into the petcock. A worn valve will cause your petcock to leak fuel while in the RUN position.

HCP109 OEM Selector Lever Distribution Valve. Fits all XJ550/XJ650 (except Turbo models)/750/1100 models.
$ 9.00

HCP1384 aftermarket Selector Lever Distribution Valve. Fits all XJ550/XJ650 (except Turbo models)/750/1100 models. Same as the HCP109 above but at a better price!
$ 5.00

HCP2338 OEM Selector Lever Distribution Valve. Fits all XJ650 Turbo models, and all XJ700 and XJ900 models.
$ 9.00

HCP2930 aftermarket Selector Lever Distribution Valve. Fits all XJ650 Turbo models, XJ700, and XJ900 models. Same as the HCP2338 above but at a better price!
$ 5.00


I would also replace the wave washer:


fp11) Petcock fuel position Selector Lever Wave Washer. These are usually worn out and need to be replaced whenever you go into the petcock. This spring washer fits in-between the selector lever and the outer faceplate, and provides the proper spring-pressure against the selector lever to properly engage the distribution valve.

HCP107 OEM Selector Lever Wave Washer. Fits all XJ550, all XJ650 (except Turbo), and all XJ750 models.
$ 2.00

HCP2918 OEM Selector Lever Wave Washer. Fits all XJ650 Turbo, all XJ700 models, and XJ900 models.
$ 1.50


and the selector lever o-ring:


fp13) Petcock fuel position Selector Lever O-Ring. These are usually worn out and need to be replaced whenever you go into the petcock. This o-ring found into the groove along the outside of the selector lever.

HCP108 OEM petcock Selector Lever O-Ring. Fits all XJ550/650 (except Turbo models)/750/1100 models using the original petcock.
$ 5.00

HCP2339 OEM petcock Selector Lever O-Ring. Fits all XJ650 Turbo, and all XJ700 and XJ900 models using the original petcock.
$ 5.00



And I would do all the things that worked for Schmuckaholic, namely:

surface the back of the selector lever flat (as well as all other gasket mounting surfaces and langes), and replace the vacuum diaphram o-ring assembly, etc. Or you can send it to me, I can rebuild them correctly and guarantee that they won't leak:

fp18) Original petcock Rebuild Service. Send me your poor, your weak, your leaking-like-a-proverbial-sieve original Yamaha XJ550, XJ650, XJ700, XJ750, XJ900, or XJ1100 petcock and we'll have it professionally rebuilt to like-new condition. Includes internal cleaning, re-surfacing of all mating flanges, align-bore and honing of the plunger mounting seat, and the replacement of all worn seals and the vacuum diaphram assembly, as well as a replacement filter and final testing. GUARANTEED TO PERFORM CORRECT AND TO NOT LEAK!

HCPPRS Petcock Repair/Rebuild Service. You must send us your old petcock via USPS or UPS and we will rebuild it. Return shipping charges are NOT included in the price.
$ 49.95

NOTE: if your petcock is not an original Yamaha unit, we cannot repair it. Also, if your petcock has broken or missing or damaged pieces (besides seals and the vacuum diaphram assembly), then additional charges will apply for replacement of damaged or missing parts.


http://www.xjbikes.com/Forums/viewtopic ... t=120.html

 

Suggest a repair Kit Here: https://www.partsnmore.com/cat_index.ph ... egory=carb
A whopping $16

OR try MikesXs. com for a ..Brand New.. non vacuum petcock for $38

 

Dang...just looked at all the pictures, and realized my petcock is not original....but still leaky!

 

I believe the ones from Mike's XS will not fit XJ tanks......different bolt hole spacing..........

 

Okay, I just read a lot more about this whole problem, and decided my petcock is the same as an original....just missing one part....the selector gasket....

No wonder it leaks!

 

Does anyone know where I can get the selector gasket for my bike? Any way to measure and be assured I am getting the correct part?

 

The HCP109 and HCP1384 distribution valves are 22.60mm id diameter.

The HCP2338 and HCP2930 distribution valves are 28.50 mm in diameter.

I have all of them in stock!