Leaking Petcock

Hello everyone. I'm new to the forum.
Been here a few times since getting my bike though, Great Site!
I have a Xj650 Maxim.

I am currently having a problem with my petcock on my bike.
It's leaking as the title describes.

I have also reviewed bigfitz's write up on a petcock pretty thoroughly.
http://xjbikes.com/Forums/viewtopic/t=25058.html
Very good job btw!

It is leaking from the diaphragm/diaphragm block. I get vacuum in the petcock when I start the bike and the valve opens. And when the bike is off it closes and seals properly (I think) and doesn't seem to leak. Even when i had the gas line off and the petcock set to on no fuel seems to come out while the bike is off.

so the diaphragm seems to be sealing enough to get enough vacuum to open and then close. However while the bike is running if you look at the the petcock you can see gas slightly spitting from what looks like the passage on the diaphragm block.

This is what i have done so far. Complete disassembled and cleaned. I dressed the two mating surfaces of the diaphragm. And reassembled everything. I was hoping I might be able to fix it with out buying anything but no luck.

I think if I got a new diaphragm it might fix the problem but if the diaphragm block is toast then I don't think it'll fix it. My thought is that since I need to buy parts anyways, may as well just buy a complete rebuild kit.

Thoughts?

 

Dark-Farmer,

Welcome. Sounds like the o-ring just behind the lever switch plate is worn. I had the same problem. While some might suggest buying a new petcock I suggest purchasing the rebuild kit. Thing is...there is a inner washer that comes with the kit that is not manufactured like the original tapered seal so a separate metal washer is added behind the plunger spring to help the washer that comes with the kit seal better. I haven't had any problems but I sniff my oil on a regular basis to insure no leakage into the crankcase. In addition to using the rebuild kit you could add a briggs and stratton or similar shut off valve per Rickomatic's write-up.

Gary

 

The diaphragm itself is leaking. If fuel is coming out of the vent in the block, then there is fuel getting on the "wrong" side of the diaphragm.

Too bad, because it sounds like it's basically working (shutting off fuel when there's no vacuum.)

Sounds like a good candidate for a rebuild. Oh, and the "booster" washer for the diaphragm spring isn't always necessary.

 

I thought it was the diaphragm.

Maybe a couple more questions, if you will.
Is the block itself ever the problem? (I'm probably going to buy a complete rebuild kit that comes with a new one anyways but I'm still curious)

Also how tight should I be tightening the cover retaining screws?

Also in the write up it mentioned silicone grease to the rubber pieces.
Would this include the diaphragm?

 

DF,

You did say it was leaking from the diaphram block. Sorry bout that. Thanks for the save BF.

Gary

 

Anyone know about the cover retaining screws?
I want to make sure i don't potentially over tighten them and ruin any new parts.

 

Use a small screwdriver and tighten them "snug", maybe only as hard as you can turn the screwdriver with one or two fingers. Every surface has a gasket so sealing isn't really an issue with such low pressures. The face plate should have a wave washer between it and the selector lever to ensure the selector lever is properly pressured against the distribution block/rubber.

I would definately suggest rebuilding it. I got the standard full rebuild kit from chacal and there was a world of difference between the new rubber and old rubber.

 

Alright sounds goo thanks for the help guys.
I'll be sure not to go to town on the screws.

 

15 bucks - cheap fix -

http://www.ebay.com/itm/400421919555?ss ... 1423.l2661

 

Here is also a pretty good video showing the disassebly/reassembly process.

The petcock on your xj is the same idea, so the assembly/disassembly is pretty much identical.

http://www.youtube.com/watch?v=5DqvB_5gP20

 

When I rebuilt mine, it didn't seal when the engine was off. I added the washer and it still wouldn't seal. Chacal suggested that I insert the plunger in a 3/8 inch socket and very-very slightly tap the other side to create a very slight dimple in the metal backing. that solved the problem for me. Apparently some of the after market diaphragm plungers are a little shorter than the original--hence the use of the washer to apply more pressure. But if that doesn't work, the "dimple" method will.

 

I took the petcock apart 1 last time before I bought parts. Besides the vacuum diaphragm everything looked top notch. Almost as someone had done a rebuild on it previously with a kit that just didn't have the vacuum diaphragm.

So I bought a deluxe vacuum diaphragm kit (the one with the spacer) from Chacal. Installed now, no more problem.

So problem solved, and thanks to Chacal!