Petcock/fuel valve question

Early last winter I rebuilt the petcock for this 650 that I'm working on. I've studied BigFitz's tutorial and have done a couple of them now. However, when I put this one on the tank with the lever in the "On" position, fuel just poured out of the outlet. Neither the fuel line of vacuum line were connected.

Might I have screwed something up on the rebuild, or is there something I don't understand about how these things are supposed to work? Thanks.

 

No.
That's a fairly common problem.

Primarily related to the "Kit" not being OEM.
I've rebuilt Petcocks for people who bought a kit from the aftermarket.
After several attempts that resulted in failure; I studied the problem and determined that Non-OEM Kits actually DO NOT fit and needed alteration.

I did contact the Manufacturer of the OEM Kits to see if a Bulk Purchase was possible.
Answer: No.
They are contractually obliged to sell to Yamaha and Yamaha alone.

Rather than argue about Non-OEM Kits tending to Leak.
And, ...
Not willing to recommend that someone spend several hours of intensive restoration work to rebuild a Petcock with the possibility of all that time and energy getting wasted because the thing leaks worse than it did before getting rebuilt, ...

I tell everyone to just, ...

Buy yourself a Brand New Petcock.
(The Old one you're replacing went over 25-years).

 

If it sat for a long time before you put it in service, it might just be stuck. Smack it against your hand a couple of times and be sure the plunger is moving inside.

For whatever reason, the plunger isn't seating the o-ring into the valve seat correctly.

If the thin metal washer on the backside of the plunger isn't "square" (at exactly 90*) to the plunger itself, it can cause the plunger to go in crooked enough to not seat properly. This is usually a problem with the "large-body" petcocks rather than the 'standard" type like you're dealing with, but it's a place to start.

Also, did you inspect and polish the seat? If it's pitted, it won't want to seal with the new o-ring.

 

Fitz-

Considering I already can't remember what I had for breakfast, recalling the specifics of the fall rebuild is iffy at best. I'm quite sure that I would have been very thorough, however, and I'm aware that pitting inside that seat would be a problem.

I think I'll pull it off, take it apart, and inspect it before I do anything drastic.

Rick-

I appreciate your response and hearing about your experiences with many of these. Because this bike is meant for resale, I'm not going the extra mile like I would with my own cycle. I need to be careful about how much money I've got sunk into it, so I'm going to futz with it a bit before I consider buying a new petcock.

Thanks, guys.

 

Finally got to pulling this petcock, disassembling and inspecting it. I can't really see anything obviously wrong. The little wafer disc is moving when I suck on the vacuum nipple. I'm getting some air when I suck on the fuel nipple, though. Does that indicate a problem? Is there some other test I can perform before putting it back on?

 

I just rebuilt mine according to Fitz's rules (literally just finished). If you can get air through the fuel nipple, then I would say there's a chance there's a problem. I can't get anything at all.

 

not that I have anything to add to this discussion being fairly new to the world of XJ but in the running feed of recent topics this was listed as pet(censored)/fuel valve question..... I guess the auto filter doesn't like the word 8O

 

The Rebuild Kits that came to me from various sources did not fit.

The Disc upon which the Small Cylinder and O-ring is mounted was too large in Diameter.
The Cylinder and O-ring could not possibly get "Seated" (Fully seated) to completely shut-off the Fuel Flow.
Pressing a bend into the thin Disc to move the Cylinder closer to the seat seemed to be a work-around.

Prompting this:
http://xjbikes.com/Forums/viewtopic/t=1 ... k+fix.html

 

i have an additional question...i bought a rebuild kit for mine, everything is going fine except for the life of me i can not get the fuel lever to seat back into the housing. I don't know if theres a secret to getting this lever back in there, or if i'm simply not pushing hard enough (can't imagine how i could push any harder though). I don't want to mess with it too much for fear of damaging the o-ring.

any ideas / suggestions?

 

Do not push too hard. You WILL damage the o-ring. The secret is lube. This made a huge difference for me--get some silicone grease and grease up every rubber piece lightly. It will go together snug, but everything will still move properly. Makes a world of difference. Like I said above, mine is presently air tight.

 

Lube it up and "rotate" it in; it should fit but nice and tightly.

This assumes you used a "proper" rebuild kit and have the correct o-ring.

 

yea, its the right kit and o-ring. unfortunately i tried to muscle it in there and put a little tear in the o-ring so i'm gonna get a new o-ring and then try the lube idea.

thanks for the advice guys

 

Hey, Rick. Is this one of the rebuild kits that doesn't fit?

Keyster K-943 Petcock Kit

 

Just edited that last post with a link. Not sure why it wouldn't embed the image file address...

 

I hope this isn't too far off topic . . .
Doesn't silicone grease cause slight swelling of rubber gaskets/ o-rings?
Is that desired in the petcock rebuild?

 

It seems like it causes some swelling to me. If you have the correct o-rings though, I don't think it's enough to be a problem. I was able to get mine together fine, and this goes for other areas of the bike I've used it on too. They're just snug, but smooth.

 

I ordered a diaphragm from Chacal and the petcock is now working. Although I couldn't see any obvious difference, the o-ring on the one from Chacal might have been just a hair smaller.

In retrospect, I wish I had put a little silicone grease on the other (Keister) diaphragm and tried it again. When I removed it, I could see that it was rather stuck to the plastic plate. Still might not have made any difference. Either way, you can't go wrong with the one that Chacal sells.

Thanks to all who replied.