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Rebuilding Yamaha Vacuum Operated Fuel Valves (Petcocks.)
- Thread starter gggGary
- Start date
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- carburetors how to maintenance tech
Xj less you do extensive testing yourself you will just have to take SOMEONE's word on it. I am good with my epoxy job but the petcock hasn't seen fuel yet. Even with no glue the 90 is a snug fit in the body so it's not likely to pour fuel. After all the stock whatever it was in there has usually turned to mush and I haven't heard of any catastrophic fuel leaks. just an annoying wet petcock is the usual symptom. I'll report back in 30 years on how my epoxy job held up. Sooner if it fails!
Well yes, but I'm not gonna take some random guy's word on it, not to mention when it contradicts some other random guy's word on it.
I was thinking JB Kwick might be a better choice than the wELD because it breaks down at a reasonably low temp if you wanted to torch it loose again - eg. if it was sticking yet leaking again.
"stock whatever it was in there has usually turned to mush and I haven't heard of any catastrophic fuel leaks"
I've discovered in long range riding things you wouldn't expect do happen. My starter gear cover plate decided to loosen up and dump a good portion of my oil, for example. Shorter trips you would notice something developing and catch it first. A blown petcock elbow squirting gas seems like a possible thing to me.
I was thinking JB Kwick might be a better choice than the wELD because it breaks down at a reasonably low temp if you wanted to torch it loose again - eg. if it was sticking yet leaking again.
"stock whatever it was in there has usually turned to mush and I haven't heard of any catastrophic fuel leaks"
I've discovered in long range riding things you wouldn't expect do happen. My starter gear cover plate decided to loosen up and dump a good portion of my oil, for example. Shorter trips you would notice something developing and catch it first. A blown petcock elbow squirting gas seems like a possible thing to me.
Then make a phone call. Simple
No one here knows if there is a petrol resistant thread tape. A quick google and a couple of threads from forums indicated there is a possibility that there are some out there.
Now if you want to find out for sure then do some research, ( i am sure a phone call to a reputable bike or car service center would get you an answer), and not make half arsed comments about some random guy and another random guy because that is what you are, just another random guy. Why would any one want to take your word for anything. Simple simple.
And if you ever want to be useful rather than pretending to be useful in your annoying way find out if "chacal" has kits for the xs650 petcock. "Chacal" as in:
"chacal the best source out there for this stuff; a lot of the other kits on the market simply don't work."
"chacal the best source out there for this stuff; a lot of the other kits on the market simply don't work."
Here's my advice on rebuilding this petcock, for you to consider. Do not buy a rebuild kit. Go through the steps above regarding cleaning and etc. Unscrew the vacuum barb and replace it with a short screw with the threads coated with seals-all. Coat both petcock halves with seals-all and screw them tight without diaphragms or the wafer and let it sit overnight. Use an inline knob as your off position. "Run" will stay the same and reserve can be either reserve or prime.
In my experience, the problem with the Special petcock is getting a pintle o-ring that will seal. The one that comes with the only rebuild kit I know of did not seal for me. While you try various o-rings the diaphragm takes on the characteristics of a used gasket. I ended up using the kit, with my old o-ring, since the original problem was the diaphragm, and it worked fine for awhile. I have always failed to find a new o-ring that will seal, even when they look identical to the original. You can stretch out the spring to give it more power, and it may seal except when the tank is full, when it will drip.
I recently had a diaphragm hole and leak that I thought was a loose elbow. It turned into a steady drip and I fixed it for the time being using "seals-all". Gasoline here is just whatever. No Shell station on the corner. In fact the higher octane gas up here seems to have a higher percentage of ethanol. It raises the octane or octane equivalence.
In my experience, the problem with the Special petcock is getting a pintle o-ring that will seal. The one that comes with the only rebuild kit I know of did not seal for me. While you try various o-rings the diaphragm takes on the characteristics of a used gasket. I ended up using the kit, with my old o-ring, since the original problem was the diaphragm, and it worked fine for awhile. I have always failed to find a new o-ring that will seal, even when they look identical to the original. You can stretch out the spring to give it more power, and it may seal except when the tank is full, when it will drip.
I recently had a diaphragm hole and leak that I thought was a loose elbow. It turned into a steady drip and I fixed it for the time being using "seals-all". Gasoline here is just whatever. No Shell station on the corner. In fact the higher octane gas up here seems to have a higher percentage of ethanol. It raises the octane or octane equivalence.
here's a pic of the throw in the towel modification. The two halves have a fel-pro gasket piece recommended for fuel pump mounting. The two halves are also coated with Seal-all, good stuff around fuel. The vacuum port is stuffed with a stubby screw, threads coated with Seal-all.
The original screws would have worked fine, but one of the heads was stripped and these were easier to find. Note - if you get replacement screws for something make sure they go all the way through the thing, using all the threads available, else it's likely to strip eventually. Also note that the front plate on the petcock uses the same dia screw as the flasher lens
Don't throw away the plastic wafer normally between the two halves, as it's hard to find.
The original screws would have worked fine, but one of the heads was stripped and these were easier to find. Note - if you get replacement screws for something make sure they go all the way through the thing, using all the threads available, else it's likely to strip eventually. Also note that the front plate on the petcock uses the same dia screw as the flasher lens
Don't throw away the plastic wafer normally between the two halves, as it's hard to find.
kfamily2003
XS650 New Member
I googled chacal but could not find anything that looked like it was related to petcock rebuild kits. Where did you find the rebuild kits? I am also looking for in tank filters for the petcocks. Any information would be appreciated.
MikesXS sells rebuild kits, I used a set of Mikes kits on non vacuum petcocks, so far so good, the polishing step is best practice for long term leak free operation.
Testing 2 type of thread tape today to see if it can be used on threads that are exposed to fuel. Non Ethanol
One is normal tape used in every day situations and the other is "TBA Permanite GT Gas Tape", (Yellow roll). I wrapped them around the threads of 2 bolts and immersed them into a container of fuel and let them sit till the fuel evaporated, about 3 hours.
The normal tape went opaque straight away but was still holding together after the 3 hours. The gas tape didn't change color at all and didn't seem to be affected at all.
In a pinch i would use either tape in an emergency, but would change the normal thread tape as soon as practical, but the Gas thread tape i think could be used without any consequences.
I have not used the gas tape , or any tape for that matter, on my carbs anywhere. I have done this in answer to questions and statements posted earlier in this thread.
One is normal tape used in every day situations and the other is "TBA Permanite GT Gas Tape", (Yellow roll). I wrapped them around the threads of 2 bolts and immersed them into a container of fuel and let them sit till the fuel evaporated, about 3 hours.
The normal tape went opaque straight away but was still holding together after the 3 hours. The gas tape didn't change color at all and didn't seem to be affected at all.
In a pinch i would use either tape in an emergency, but would change the normal thread tape as soon as practical, but the Gas thread tape i think could be used without any consequences.
I have not used the gas tape , or any tape for that matter, on my carbs anywhere. I have done this in answer to questions and statements posted earlier in this thread.
flthead
XS650 Addict
heres the link to universal fuel petcock set up http://www.650motorcycles.com/Petcock.html be nicce if someone here coulddo the adapter plates reasonable not 30 bucks each like here https://www.denniskirk.com/3-8-in-npt-44mm-adapter-plate.p181576.prd
Here's the adapter plate for 7 bucks, but the shipping'll get ya.
Scroll down. 46mm is the most common for our apps.
http://www.partsnmore.com/parts/honda/cb750/?filters[category]=carb&filters[fitting]=universal
Scroll down. 46mm is the most common for our apps.
http://www.partsnmore.com/parts/honda/cb750/?filters[category]=carb&filters[fitting]=universal
nj, it gave me $122 for shipping to Aus: 
For that price i would rather do the throw in the towel mod
For that price i would rather do the throw in the towel mod
nj, it gave me $122 for shipping to Aus:
I'm back in the mode for completeing the vacuum to manual conversion.....now where did I leave those parts and pieces.....
flthead
XS650 Addict
shipping was only 13.95 to nj
Reasonable. Need to check the spacing of the mounting screws before placing any pre-drilled plate orders. My '77 is a bit smaller than the '83 on the spacing. It's a relativly easy mod- just need to open the tank a wee bit for the aftermarket petcock.....quarter/half round or a rat-tail file. Don't need to take a lot out, just enough.
Note.....don't file with the plate on, you'll fek the 3/8 npt threads.
I snatched a pingle? petcock off eBay for around 15 bucks...add 20 or so for the plate. Competative pricing.
