Petcock Leaking in ON Position

When I say leaking, I mean a FLOOD of gas comes out the fuel line part. Holy crap. I didnt have this problem when I took the gas tank off close to a month ago to work on the carbs.
So it was leaking just a tiny bit when i was putting it back on its rack, and I had it tilted up so I could attach the lines. And when I set it down to re-attach the bolt the line filled with gas and flooded the crap out of my carbs, leaking everywhere onto the ground. Not cool dudes.. So i took the gas tank off again and turned the drain screws on the carbs to let the gas out. The airbox smells like gas, the crankcase does not. Which is good! I think.. I just bought that filter too.. dang.. I'm goin back out to check the plugs in a min and see if they got fouled.. Hope not.
I took the petcock apart and cant really see any debris in it. The gasket to the vaccum line looks ok. O-ring looks ok... What am I doing wrong!?!? I was just about to start her for my first time too!!!! :evil:
Any ideas or suggestions before I rip some hair out??
-SLKid

 

SL, did you have the little spring that goes between the housing & the diaphragm that the vac opens to allow fuel flow? If no spring or spring is severely compressed, that could be your problem.

 

I had this problem, the o-ring in the selector valve was shot. I assume this is the one you're talking about, since the huge o-ring wouldn't cause this problem.

Were all the pieces of the petcock there? Most importantly is the wave washer that actually controls the flow of fuel, and is easy to lose or overlook when reassembling. That's 16.

Hopefully this diagram is relevant to your model, I only have this one. If not, then ignore me!

 

I do indeed have the spring. It may be compressed, i'm going to clean it up with carb cleaner and reassemble the Petcock. And yes. The "wave washer" is there. It looks slightly bent though. I'll straighten it out and put it back on. 18 is the O-ring for the valve correct? and 14 is the part with the rounded grooves right? Sooo... I dunno.. I'll go check those few things and report back. I hope the plugs arent fouled. Man this blows. Its always somethin huh? Would #20 be the reserve tank??? If not, what is it? Thanks for the help guys. I'll let you know how it goes
-SLKid

 

18 is the oring that goes on the change lever, 20 is the intake filter for the petcock, not to be relied on instead of an inline filter. On the spring issue if it is compress & won't apply enough pressure on diaphragm you can put a small washer behind it. That will increase the pressure applied by the spring. I had a leaking problem on mine as well, it took 2 wahsers to get mine to stop leaking. This was after I rebuilt the petcock.

 

You mean, put a washer or two behind the spring to make it compress more? Sounds reasonable.
I cleaned all the parts except the filter cause I didnt wanna detach it, and flipped her over. She was fine, so i moved it again, sloshed a bit around. Fine. Turned her around to look at the other side where the vac hose is and sloshed again a bit. Started leaking again when I tilted her about 20 degress past level. Wierd.... It leaks like crazy even at Level position when I turn it to anyhting but ON. So, RES and PRI leak too.. Whats up?? Goin out now to check plugs. Needed tools... Man..
-SLKid

 

What happens after time the spring sits in a compressed position for a long period of time which allows the spring to set in that compressed state. Meaning the spring is no longer as long as it was when new & not applying as much pressure on diapragm as when new. By putting the washer or washers behind the spring it will apply more pressure on the diapragm keeping it sealed until opened by vac from carbs.
With it set on PRI it will flow fuel continuosly, the spring/diapragm have no effect when in that position. RES position should not leak though.

 

And DON'T "straighten" the wave washer (#16)....it's supposed to be wavy!!!

 

So, hopefully after the washer installation the problem should be "fixed". Hopefully, anyway. Thanks chacal. Its a shame you caught me AFTER i tried to bend it. It wouldnt bend after one or two tries so I said F it and installed it anyway. Is it suppossed to be installed a certain way btw? Lined up with something on the knob or the metal behind it?
Plugs checked out, not fouled. Airbox smells like Filter Oil, thank goodness. Crankcase still smells of delicious 10w40 still. Awesome. So hopefully an easy fix.
It appears, btw, that the PO moved the petcock position. There is an old mount for a petcock all glued and sealed off about 6" up from where my petcock is now. I wonder why that is. I'll take pics when I'm off work tomorrow. Thanks guys. I appreciate the posts and help.
-SLKid

 

I had mine leak last year, but just once. I assume I should rebuild it soon. Instead of going thru the hassle of draining the tank and removing the petcock, I just ran over to a hardware store and got a small shut-off valve (used on lawn mowers) and put it inline just after the petcock. Now it can leak all it wants to. It's just a matter of shutting off the gas now.

 

If you install a shut off valve, when you turn it on, wouldnt it still flood the carbs? Thats what happend to mine. It was on, and flooded all the carbs at an alarming rate. So, the shut off valve wouldnt stem the flow of gas coming from the petcock. Would it???

 

You must have a bad float problem if gas "runs" out of them. I just turn the shut-off valve on before I start it and shut it off when I park it. I never seen any problem with using one, they used to be on all the older bikes. Mine won't stay running long if I don't turn it on, so I don't usually forget.
Mine leaked only once, but it was once too often. It left a small spot of gas on the shop floor (unexeptable) and thankfully, didn't let any gas into the crankcase.

 

No, see, when the petcock is ON, it needs a vaccum to suck it into the carbs right?? There's no vaccum. It just leaks into the carbs, overfilling them to the point of flooding.

 

Is it in prime? Prime will free flow without vacuum. I bought the basic fuel valve kit from chacal a few months back, took the 30 minutes including the surface honing and prep and rebuilt it. It works so nice and is smoother than butter now. Well worth the time and money.

 

No sir. Not in prime. As stated, when in prime it leaks like a river even when held Level. Res does the same thing. ON position works.. until tilted anything but Level. Think it could be anything else but that spring?

 

If it is just leaking from the fuel access only, the vacuum diaphram is stuck open or the rubber valve with the 4 holes in it is not seated correctly.

 

Yes and no.
The vacume pulls the diaphragm back allowing fuel to pass by.
Yes, with no vacume the diaphragm should remain closed not allowing fuel to pass, in on or res position.
Even if the petcock is left in prime, so fuel flows, constantly, your needle valves should seat to cut off fuel flow in the carberator.
It shouldn't flood into the airbox, cylinders.

 

Capy, what do you suggest? The washer with the four holes I cleaned, and placed back into the valve, and made sure the holes were lined up and it "popped" into place. I dont think thats the problem.. If it's stuck open should I compress that spring more with washers like suggested, or should that spring be less compressed somehow? I'm hoping to try and start her up today! (again.. this is like the fourth time I've 'tried' to start her. Never succeding in actually gettin to press the start button)
-SLKid

 

Sadness... The washer method didnt work. Well, sorta. I couldnt find a washer small enough to fit next to the vac port so I put it on the other end of the spring. The end with the gaskets. Maybe that was a problem? But anyway, gas still leaked. It didnt leak until I put it in the same incline that it sits on the bike. It leaked really slow though! Not as bad as before. I was able to turn it to PRI and RES with only minimal leakage. Seemed normal for PRI.
There was a broken O ring though. It came out when I took the 'plunger' out, wrapped around it. I dont think its actually supposed to be on the plunger itself, but I could be wrong. I'll post pics.
So what should I do then? I'm guessing my next step is a rebuild kit. And after that, if it doesnt work, a new petcock itself. Can the Maxim have an Aftermarket petcock, or do I need a OEM one. Anyway. Would love suggestions.
-SLKid

 

SL I think you have found your problem. If that oring being broken is not sealing off the fuel supply allowing it to leak by. Replace that oring & I think your problem is solved. Lets hope. On the washer topic, I didn't have exact fit washers either, they go in the little pocket in the metal part that covers the diaphragm, I had to take a dremel & grind the outside diameter small enough to fit in that pocket. Once you hae replaced the oring put it back together & try it again, without the washer. I think you should be okay. If still leaking slightly, try the washer then.
Good luck & keep us posted
Gregg