I guess that's 1970's engineering, but seems like a crappy way to assemble a component that carries fuel. I'll try and disassemble mine this week and see what I can find. I'll figure out how to fix the vacuum petcock, but I'm still leaning towards replacing them with those non-vacuum petcocks. I don't like the idea of trusting a rubber flap to hold fuel in the tank as opposed to having the ability to turn it off when not in use. New Coke seemed like a great idea at the time too, but didn't work out so well.
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Understood I have fought a few vacuums, had to change oil THREE times on one bike! But finally won the battle, not stubborn am I?
Mikes' non-vacuum replacements have worked for me. I did a tutorial which might be helpful to you:
http://www.xs650.com/threads/instal...m-petcocks-on-later-models.50124/#post-517151
I love pictures! No left and right, correct? One petcock design, just turn it around and screw it on the other side.
I am in favor of the vacuum petcocks. If there is a leaky float valve in a carb it's not a huge deal. I know I have to address it. The only time I have to touch my petcock is on the off chance I need my reserve gas.
That's my 2¢
That's my 2¢
Correct. Just install the enclosed outlets in the correct position.
Although my recently acquired 79F suffered neglect and lack of attention to the fuel tank and petcocks causing all the petcock troubles described by members, I am going to stick with vacuum petcocks.
However, the 78E petcocks are my choice.
Those unique designed petcocks should be sought out by members who are still fans of the vacuum petcock benefits !
My own past experiences with good working petcocks is fun ! They are an interesting mechanical component which fit the style of the whole bike, and aid 78/79 BS38 carbureation design.
78E petcocks can be found if you are determined !
BTW, I am shelving my 79 "special" style vacuum petcocks until later when testing gains my trust. Not Now
-RT
However, the 78E petcocks are my choice.
Those unique designed petcocks should be sought out by members who are still fans of the vacuum petcock benefits !
My own past experiences with good working petcocks is fun ! They are an interesting mechanical component which fit the style of the whole bike, and aid 78/79 BS38 carbureation design.
78E petcocks can be found if you are determined !
BTW, I am shelving my 79 "special" style vacuum petcocks until later when testing gains my trust. Not Now
-RT
Attachments
I removed everything but an on/off switch and a capacitor, its like a frame with an engine on it, the only mechanical accessory left to go wrong was the petcocks, go figure.
The real problem is my wife complaining about the fuel smell in the garage. I told her I can soak it up with cat litter, but apparently that was not the correct answer.
Hi caj,
I've posted this before but here it is again:-
Get the best of both worlds (vacuum operation + a true OFF position) by filing the little nubbin off the gas tap plate and cutting the tap lever off short
so the lever can be turned to point straight up. Straight up is OFF.
After I disassemble the petcocks, based on what I find, I might think about it, but I still have to determine where the leak is coming from first and if I can fix it first. I appreciate all the input, I have several options to consider and it won't be warm enough to ride for months, so I'm in no rush either.
Yes, pull them apart and inspect all the rubber bits, metal sealing surfaces too. There's an o-ring on the little plunger fitted to the diaphragm assembly. That can go bad or wear out. It fits and seals into a tapered hole in the back of the petcock body. Polish that tapered seating area clean and smooth. The holes in the back side of the lever sometimes have sharp edges on them. Those can tear up the 4 hole rubber disc when you turn the lever. I "break" those sharp edges, round them over, with a small, sharp knife. You also want to polish the back side of the lever that rubs against the 4 hole rubber disc. You want it nice and smooth.
I found my 90 degree outlet had come unbonded, the glue has disintegrated, I could just pull it out. Is there any particular adhesive you recommend that would be best? The only thing that comes to mind is JB Weld, but not sure about how resistant it would be against gasoline, and likewise, it will be a permanent modification, I guess that is alright.
I believe JB Weld is up for that repair.
JB Weld was used by myself many years ago in attempt to "glue" a petcock into a stripped screw in mount hole on a plastic off road tank. JB Weld did fail after time but only due to expansion and contraction of the plastic tank. The gasoline exposure did not seem to be the reason. Vibration ( ring ding 2 stroke) and temperature fluxuations contributed to the failure.
That is the only time remembered by me that JB Weld did not fix it.
-R
JB Weld was used by myself many years ago in attempt to "glue" a petcock into a stripped screw in mount hole on a plastic off road tank. JB Weld did fail after time but only due to expansion and contraction of the plastic tank. The gasoline exposure did not seem to be the reason. Vibration ( ring ding 2 stroke) and temperature fluxuations contributed to the failure.
That is the only time remembered by me that JB Weld did not fix it.
-R
Have used various epoxies there, none have failed... Didn't really think the type with fillers (like JB weld) is needed here. 
As always clean, clean, clean, before gluing is key. Scrape any remaining old glue out of the little groove in the nipple, I think this is key to a permanent repair.
As always clean, clean, clean, before gluing is key. Scrape any remaining old glue out of the little groove in the nipple, I think this is key to a permanent repair.
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I've had that problem on other Yamaha's. I use gas resistant Teflon tape. I put two or three wraps on the tube and press it in while twisting with protected pliers. It usually takes a couple tries to get the right number of wraps of Teflon tape and to be sure that the tape is entering the petcock body. Works great with a little finesse.
Scott
+1 on JB weld....I made an aux fuel tank to hang above the bike for tuning purposes (so that I could remove the bike's tank but still have a running engine and get to carbs, etc)...I made it out of an aluminum water bottle...drilled a hole in the bottom, put in a ball valve w/lever type fitting from hardware store as the on/off fuel shut off and various hose lines off the end. The fitting was fairly tight, but I used JB weld to seal it, and it's been sitting in fuel (for the most part) for over 3 yrs now...no leaks/issues. BTW, the top of the water bottle has that pull-up type action to drink from, but I use it as a vent to flow fuel. Works pretty good. Only paid a $1 at 2nd hand store. 
