Petcock Advice

[Lluber]

Hey guys,

Yesterday I put my carbs back on after rejetting.. get everything hooked up and ready to go and Splash, Im leaking gas from the left engine case. Its a oil, gas mix. I pull off my left side cover and fuel and oil are leaking out from under the rotor. I pull my oil plug and I've basically been storing gas in my oil pan.. I've got it all drained out and letting the rotor area dry out as much as possible now. Seems my vacuum petcock is to blame here.

Question I have is, should I go with the more classic on/off style petcock or do I rebuild my vacuum operated petcock?

I've found a very extensive and detailed rebuild link HERE im just looking for pro's cons on going with a on off vs the vacuum style. Thanks and any advice tips anything is appreciated.

 

[retiredgentleman]

Hey guys,

Yesterday I put my carbs back on after rejetting.. get everything hooked up and ready to go and Splash, Im leaking gas from the left engine case. Its a oil, gas mix. I pull off my left side cover and fuel and oil are leaking out from under the rotor. I pull my oil plug and I've basically been storing gas in my oil pan.. I've got it all drained out and letting the rotor area dry out as much as possible now. Seems my vacuum petcock is to blame here.

Question I have is, should I go with the more classic on/off style petcock or do I rebuild my vacuum operated petcock?

I've found a very extensive and detailed rebuild link HERE im just looking for pro's cons on going with a on off vs the vacuum style. Thanks and any advice tips anything is appreciated.

There's only one answer................buy a new manual petcock. That's all I have ever used on bikes. Vacuum petcocks don't have an "off" position, which leaves the possibility of bad things happening, as you are finding out.

 

[Lluber]

I read on another thread you picked up the manual petcock from mikes, good? and what I would need to add one of the filters that fits over the intake tube of the petcock?

 

[weekendrider]

The plastic slip overs will soften, deform and split with ethanol blends.
An inline filter is a better option in my simple mind.

 

[retiredgentleman]

I read on another thread you picked up the manual petcock from mikes, good? and what I would need to add one of the filters that fits over the intake tube of the petcock?

Yes, the manual petcock from Mikesxs works very well. I use the 90 degree type of filter that www.650central.com sells. They allow easy routing of fuel lines.

Don't waste money on those filters that slip over the petcock intake tubes. The vibration from the bike cause those to fall off. Found mine laying in the bottom of the fual tank..................that's when I bought the 90 degree inline filters.

The manual petcocks have a fine screen inside the petcock itself. The screen is open at both ends, so I pinched one end and soldered it closed.

 

[deadchef]

i replaced mine with mikes manual shutoff. works fine and i always turn it 'off' when i park. no worries about being stranded somewhere with a case full of fuel.

 

[gggGary]

I still like vacuum petcocks If they can be rebuilt to work correctly or get new one. But I'm lazy. The thing is you can get a new manual petcock for about what a rebuild kit costs and rebuilds don't always fix leaks. No petcock manual or vacuum has a guaranteed off. Always check your oil level and smell the dip stick after a layup. I think a pre-petcock screen is a good idea also, hate to have a chunk of rust from the tank tear up the petcock seals.

 

[jetmechmarty]

Hey guys,

Yesterday I put my carbs back on after rejetting.. get everything hooked up and ready to go and Splash, Im leaking gas from the left engine case. Its a oil, gas mix. I pull off my left side cover and fuel and oil are leaking out from under the rotor. I pull my oil plug and I've basically been storing gas in my oil pan.. I've got it all drained out and letting the rotor area dry out as much as possible now. Seems my vacuum petcock is to blame here.

Question I have is, should I go with the more classic on/off style petcock or do I rebuild my vacuum operated petcock?

I've found a very extensive and detailed rebuild link HERE im just looking for pro's cons on going with a on off vs the vacuum style. Thanks and any advice tips anything is appreciated.

Whether you rebuild the petcock or replace it, you still have not fixed the problem. If you have gasoline in the crankcase, your float valves are leaking as well as the petcock. Fuel should not be getting by the float valves with the engine off regardless the petcock position.

The probable best fix is to replace the needles and seats, and make sure the floats are set properly. You may have luck cleaning the float valves, or just the seat and replace the needles. Mike's XS has just the needles for $5 ea. I had this issue and replaced the needles and seats with OEM, then properly adjusted the floats.

The OEM petcock on this motorcycle is a good quality item. I don't know anything about the Mike's valve. If you follow that link that you posted from XJ Bikes.com you will have complete success rebuilding your petcock. I have successfully rebuilt them. I also have an SK that I bought new. The petcock works fine and I've not touched it.

I bought my rebuild kits from George Fix. He provides a good product and fast service, but there are several sources for these parts. Don't fix the petcock and drive on. You need to fix those leaking carburetors.

 

[weekendrider]

jetmechmarty,
Don't you feel you are the "exception to the rule" ?
I see very few posts saying my oem petcocks work fine.
To replace them with a manual kinda nips everything else in the bud.
You don't have problems if you turn it off and run it abit(I try to shut them off a block or so before I stop).
Be it the rubber o-ring or the valve tip leaking.

 

[mrtwowheel]

Whether you rebuild the petcock or replace it, you still have not fixed the problem. If you have gasoline in the crankcase, your float valves are leaking as well as the petcock. Fuel should not be getting by the float valves with the engine off regardless the petcock position.
:

Not true, a leaking vacuum diaphram will cause fuel to be sucked right into the engine. Float valves are not a factor.

Change the petcock, don't rebuild a poorly and stupidly designed system.

Scott

 

[jetmechmarty]

Scott,

You are wrong. The petcock is a valve that is either open or closed. It is the same whether it is manual or vacuum operated. The float valves should be controlling how much fuel gets into the bowls. If the floats are properly adjusted and the needle/seat arrangement is not leaking, fuel will not get into the oil. (unless the spark plug doesn't work and/or the mixture is extremely rich) Turn the fuel on, once the bowl is full, no more fuel should flow.

As far as the rebuild goes, if the parts aren't corroded and you take the time to do it right, the vacuum valves work fine. If you just throw a kit in it, you will have limited or no success. The rubber seal might be susceptible to ethanol damage, but the manual petcock will have rubber parts in it too.

If a manual petcock makes you happy and secure, then by all means, go that route. There isn't anything wrong with it, so long as you remember to turn it off. If you don't fix the float valves, you will continue to dilute the lubricating oil with fuel.

 

[weekendrider]

jetmechmarty as yours work you probably haven't seen gas come from the vacuum line.
But some of them do leak and if the built in weep/relief hole is plugged the gas goes down the vacuum line not through the carbs. Direct route, all downhill.
At least with the manual the hydrostatic pressure has to push it down past the float valve and back up around the slide needle. Before that you will notice it coming from around the faceplate.

 

[jetmechmarty]

As I said, there's not a thing wrong with switching to a manual petcock. Also, if Lluber follows the detailed instructions in the link he provided, there is no reason he can't successfully rebuild the vacuum unit if he prefers it. It can be fixed either way.

weekendrider, I see your point. That is easy to check. If there is evidence of fuel in the vacuum line, that means the little o'ring is not sealing AND the vacuum diaphragm is torn or has holes in both layers. If that isn't the case, he has to fix the needles and seats as well as address the petcock.

Scott, if the vacuum line is sucking fuel as weekendrider suggests might happen, then you are right and I stand corrected.

 

[mrtwowheel]

Scott, if the vacuum line is sucking fuel as weekendrider suggests might happen, then you are right and I stand corrected.

Been doing this for a long time, I don't guess at anything. Confidence is a good tool to have.

 

[xjwmx]

There is an excellent thread here started by gggary on rebuilding the vacuum petcock. You can get the parts from z1enterprises.com. It is a little bit touchy.

I rebuilt mine once and it lasted for a couple of years. I did this and that to it for another year or so to keep it working. It's not a bad system, but it requires perfect parts.

So, to avoid another surprise leaking this or that I performed radical but cheap surgery I call it the throw in the towel mod. Go to autozone or napa and get some auto carb gasket cardboard and a tube of stuff called seal-all and an inline fuel valve (lawn mower section). Remove the plastic wafer from the petcock and the two diaphragms and put the two metal haves back together with the cardboard and the seals-all. Plug the vacuum port on back of the petcock with a short screw coated with seals-all. Put the inline valve after the petcock. Your new run position is still run and your reserve position is either prime or res, you have your choice. This is my permanent solution. No Chicom shit replacement valve to wear out next week, and just head on down the road. Carry a spare inline valve ($5).

 

[Lluber]

Im used to having a on/off petcock. I have one on my cb350 so It was weird for me to get used to the vacuum style of the xs when I first got it. Because I'm still learning and carbs seem to be the bane of so many issues. I didn't change anything around the float heights or needle's I believe my 83" has non adjustable needles anyway. I understand that maybe the floats aren't seated properly or that maybe the tang for the needle height might have changed slightly when I pulled the bottom off the carb body but I don't think its my float height thats the problem. I'll double check them tonight with my micrometer to be 100% and they should be 22mm +/- 1mm based on the carbguide ( i have the plastic floats). Retiredgentleman and weekendrider have always given spot on advice for just about everything I've had issues with. I'm inclined to listen to both of them and just swap my petcock.

 

[Lluber]

ohh yeah, any idea of negative effects of the oil fuel mix coming out near my rotor? I can't imagine its good. Im guessing I should carefully clean the face of the rotor with a soft clean rag or microfiber cloth? anything I can use to clean out the inside area? and sop up any of the liquid?

 

[mrtwowheel]

ohh yeah, any idea of negative effects of the oil fuel mix coming out near my rotor? I can't imagine its good. Im guessing I should carefully clean the face of the rotor with a soft clean rag or microfiber cloth? anything I can use to clean out the inside area? and sop up any of the liquid?

I would say, drain the oil and leave the rotor cover, drain plug, oil cap and what ever else open for a while (days) to let the gas evaporate while turning the engine a few times before adding new oil.

All of this is because the EPA is concerned about a little fuel on the ground and evaporation. When these great and worthless systems go bad there is more spillage and evaporation going on than there would be without these fruits of genius.

Scott

 

[Lluber]

yeah, I pulled it all apart and figured it would air dry.. just trying to be proactive and prevent a 10 steps backward situation.. Man, Im starting to wonder if these bikes even like being ridden.

 

[jetmechmarty]

I didn't change anything around the float heights or needle's I believe my 83" has non adjustable needles anyway. I understand that maybe the floats aren't seated properly or that maybe the tang for the needle height might have changed slightly when I pulled the bottom off the carb body but I don't think its my float height thats the problem.

Lluber,

The needle I'm referring to is connected to the float. It's the slide needle you're thinking of, and that has nothing to do with it. See if there is evidence of fuel in the vacuum line to the petcock. That should tell you something. If there is no such evidence, the float valves are suspect. The needle I refer to hangs from the float. When the fuel raises the float, that needle moves against the seat and is supposed to stop the fuel flow into the bowl. If it does not, the bowl will overflow and the fuel will go into the engine, and/or the air boxes.

Float Needle

Needle & Seat

If you find fuel in the vacuum line, that means you're sucking in a lot of fuel as Scott an Weekendrider suggest. Your petcock could be the only problem in that case. You will get there. Once sorted, this is a reliable motorcycle.