Leaking petcocks on 1979 XS650....recommendations?

[caj411]

I recently completed my 1979 XS650 build, got it running, everything seems fine, but I was smelling gas. I've figured out it looks like both petcocks are leaking, I still need to be sure its both and not just one, but its hard when its below zero temps.

Having said all that, do people here recommend rebuilding or replacing? After 30 years, I can't see trying to narrow it down to a single gasket, I probably should replace them all with a rebuild kit. I've seen some people suggest to replace the vacuum type petcocks with manual. Seems it would be safer if I could turn off the fuel, but not sure if I can use that type on the 1979 model, I assume they put the vacuum type petcock on there for a reason.

 

[5twins]

The vacuum petcocks were simply a modern update. Most all bikes started getting them by the late '70s or early '80s. They're great when they work right, not so much when they don't, as you're discovering, lol. You might be able to rebuild them. Sometimes it works, sometimes not. It depends on the condition of the metal parts inside. If they're still good, it just might take replacing a few of the rubber bits. Under the lever, there's a big rubber disc with 4 holes in it. This is what the lever seals against. Sometimes it hardens up and/or shrinks with age, or gets all torn up from the lever turning against it. I'd check that first. Many times to fix it, you can just flip it over so the unused bottom side now faces out.

When Yamaha started using the vac petcocks on the 650 in '78, the mounting hole spacing was changed from the earlier manual petcocks. That means they won't swap on. There are aftermarket manual petcocks being made though that fit. But, the quality isn't always that great. They may leak right out of the box. So, I would attempt to fix your originals first but if that's not possible, you may have to chance some aftermarket ones.

There is also a way to convert your vac petcocks to manual ones by swapping some of the parts side to side. But, if you can't stop them from leaking in their normal vacuum state, converting them may not help much.

http://en.650wiki.org/index.php/5.02.1_Vac_Petcock_Conversion

 

[650Skull]

How to and what to look for.
http://www.xs650.com/threads/rebuilding-yamaha-vacuum-operated-fuel-valves-petcocks.20662/

 

[ThatXS650Guy]

Mine leaked too after the first time I rebuilt them. After perusing the tutorial above and doing it again never had another problem with the 650 petcocks or any other for that matter.

 

[gggGary]

That guide above, I will use ONLY genuine Yamaha "valves",the 4 hole gasket, I also CAREFULLY extend the vacuum valve shaft "a little bit" by slightly bending the flat aluminum disk, placing it on a properly sized deep socket to support the rim then tapping down the center. Warning real easy to make a mess if you go too far.

 

[caj411]

As opposed to rebuilding and possible issues associated with it, what about these replacements at MikesXS?
http://www.xs650direct.com/products-34.html#product-20-0019

 

[caj411]

The vacuum petcocks were simply a modern update. Most all bikes started getting them by the late '70s or early '80s. They're great when they work right, not so much when they don't, as you're discovering, lol. You might be able to rebuild them. Sometimes it works, sometimes not. It depends on the condition of the metal parts inside. If they're still good, it just might take replacing a few of the rubber bits. Under the lever, there's a big rubber disc with 4 holes in it. This is what the lever seals against. Sometimes it hardens up and/or shrinks with age, or gets all torn up from the lever turning against it. I'd check that first. Many times to fix it, you can just flip it over so the unused bottom side now faces out.

When Yamaha started using the vac petcocks on the 650 in '78, the mounting hole spacing was changed from the earlier manual petcocks. That means they won't swap on. There are aftermarket manual petcocks being made though that fit. But, the quality isn't always that great. They may leak right out of the box. So, I would attempt to fix your originals first but if that's not possible, you may have to chance some aftermarket ones.

There is also a way to convert your vac petcocks to manual ones by swapping some of the parts side to side. But, if you can't stop them from leaking in their normal vacuum state, converting them may not help much.

http://en.650wiki.org/index.php/5.02.1_Vac_Petcock_Conversion

I don't think I want to do that conversion, the petcockas already leak, most probably due to old rubber/gasket failure. I don't think this would solve the primary problem of leaking fuel, and it just opens up a host of other possible problems. I am looking at replacing all the gaskets/rubber with a rebuild kit or buying replacement petcocks. Rebuild for $23 apiece or replace for $54 apiece. That's my current debate.

 

[5twins]

Just how are they leaking? Is fuel dripping out of the petcock itself, or passing through internally and over-filling the carbs? In either case, removing the face plate and lever, then flipping the 4 hole rubber disc over may fix it. Hey, it's free to try.

 

[fredintoon]

Fix the leaks by replacing the 4-hole rubber thing, (most likely a PO has already flipped it over) re-arcing the wavy washer and polishing the lever face.
Convert to manual by solid gasketing the vacuum actuator panel and dumping it's innards and swapping the right and left petcock levers.

 

[caj411]

Just how are they leaking? Is fuel dripping out of the petcock itself, or passing through internally and over-filling the carbs? In either case, removing the face plate and lever, then flipping the 4 hole rubber disc over may fix it. Hey, it's free to try.

I can't really tell where the leak is coming from exactly, its been too cold to get out and work on it, I just noticed the fuel smell, but its definitely coming out of the petcocks themselves. Once the cold passes I will take the tank off and remove the petcocks. I suspect its simply 30 year old rubber since both seem to be leaking, but its a very slow dribble. The petcocks were removed for the tank to be painted and I suspect the seals were damaged.

 

[5twins]

Well, then it could be where they attach to the tank. That would have nothing to do with the internal parts. They might all still be good. I think gggGary just discovered the proper size replacement o-ring for that tank to petcock mount. Maybe he'll chime in here with the info.

 

[gggGary]

I got 10 and installed one of these; vacuum type petcock to tank o-ring, 41mm ID 3mm thick
It'll work but if I order again i'll go down to 40mm ID, 41mm was just a titch long. These take a bit of pushing to get them in the groove as you tighten the screws, but I've done a bunch over the years, no big deal. I also suggest you scrape any remaining paint off the tank sealing surface. I use bit of crazy glue to seal any paint edges, cheap insurance against gas working under the paint, do this on the cap neck also.

 

[Brassneck]

For what it's worth...on my '79, I spent a little over a year addressing my leaking vacuum petcocks. Initially, I rebuilt them (simply got new rubber bits and swapped them in)...and they worked "OK" for a bit, but inevitably started to leak again...the rebuild kits just aren't that great from my experience. Being a bit more focused the next time, I took them apart and really polished the internals, made sure the rubber/gaskets were sealing good and they lasted through the summer....until they leaked again. I then got another set of petcocks from a scrap motorcycle/salvage shop in my area (sigh, they have since closed down)...and was able to mix and match parts to get them to work again for another 6 months...OEM is really where it's at. However, they leaked again and I was tired of trying to keep them going. I ordered Mikes' manual petcocks and since then they have worked without issue. The dial on them is a bit stiff, but no leaks and I can walk away without worrying. The hardest part was remembering to turn it off after riding (or turning them on about a block away from my house...ha ha).

Oh, the other nice thing is that while you have two petcocks, you only need to turn one on/off...as the carbs are connected.

I like the convenience of the vacuum petcocks...but without quality replacement parts, it's just a hassle in my opinion. Good luck which ever way you decide.

 

[caj411]

Well, then it could be where they attach to the tank. That would have nothing to do with the internal parts. They might all still be good. I think gggGary just discovered the proper size replacement o-ring for that tank to petcock mount. Maybe he'll chime in here with the info.

I just took the tank off this morning and from what I can tell, it is coming from the petcock internals or either the tit where the hose attaches. It does not appear to be the seal against the tank itself. I think I need to take them apart, see what the internals look like and go from there.

 

[caj411]

I got 10 and installed one of these; vacuum type petcock to tank o-ring, 41mm ID 3mm thick
It'll work but if I order again i'll go down to 40mm ID, 41mm was just a titch long. These take a bit of pushing to get them in the groove as you tighten the screws, but I've done a bunch over the years, no big deal. I also suggest you scrape any remaining paint off the tank sealing surface. I use bit of crazy glue to seal any paint edges, cheap insurance against gas working under the paint, do this on the cap neck also.

Thanks for the O-ring info, that will help.

 

[caj411]

For what it's worth...on my '79, I spent a little over a year addressing my leaking vacuum petcocks. Initially, I rebuilt them (simply got new rubber bits and swapped them in)...and they worked "OK" for a bit, but inevitably started to leak again...the rebuild kits just aren't that great from my experience. Being a bit more focused the next time, I took them apart and really polished the internals, made sure the rubber/gaskets were sealing good and they lasted through the summer....until they leaked again. I then got another set of petcocks from a scrap motorcycle/salvage shop in my area (sigh, they have since closed down)...and was able to mix and match parts to get them to work again for another 6 months...OEM is really where it's at. However, they leaked again and I was tired of trying to keep them going. I ordered Mikes' manual petcocks and since then they have worked without issue. The dial on them is a bit stiff, but no leaks and I can walk away without worrying. The hardest part was remembering to turn it off after riding (or turning them on about a block away from my house...ha ha).

Oh, the other nice thing is that while you have two petcocks, you only need to turn one on/off...as the carbs are connected.

I like the convenience of the vacuum petcocks...but without quality replacement parts, it's just a hassle in my opinion. Good luck which ever way you decide.

Thanks, first hand info is always the best. I was thinking it might be better to spend the $100 and be done with it than $45 for a crapshoot. Considering it worked for you, I think I'll just order those manual replacements from MikesXS. I like the peace of mind from being able to cut off the gas too.

 

[gggGary]

Many of the 90 degree outlets are glued in and the adhesive has let go. Clean well especially that little ring (you'll see it) and rebond with epoxy, should be good for another 30 years.

 

[5twins]

I had one of my petcock bodies start leaking on me several years ago. It turned out to be one of the plugs in a cross-drilling. The epoxy they used to seal it gave way. I fixed it with JB Weld and it's been good ever since.

 

[caj411]

Many of the 90 degree outlets are glued in and the adhesive has let go. Clean well especially that little ring (you'll see it) and rebond with epoxy, should be good for another 30 years.

That was exactly where I am thinking its leaking, but very hard to tell. Do the outlets screw in or is it simple glued in place?

 

[gggGary]

Just glued and prevented from turning (much) by a couple of pins. there are several designs some years have two different type petcocks left to right