petcock runs on any pos (res, on, prime)

[sly409]

So the other day I started removing my tank to drain the fuel in preparation for some tank derusting and noticed the petcock will continue to drain on any position. From my understand these petcocks are vacuum operated but mine didnt have a vacuum line so I dont know if it would apply. I did notice it had the little vacuum connector on the back of the petcock and I noticed it was dripping fuel from there. I thought the only way the vacuum operated petcocks worked was that they would not work on RES or ON unless the motor was running and that PRI was the only way to bypass that. Now I just wanted to find out if my petcock was faulty or does it sound like none of that matters because of the missing vacuum line? Thanks

Some pictures provided for reference. Left has closeup of the petcock. Right under the cock knob you see the little connector for the vacuum line and a little bit of fuel dripping from it. I dont even know if that is what the factory petcock is suppose to look like. Mine has a broken lever and is very hard to turn. When I bought the bike it came with a spare one in a box that has the lever intact and is easy to turn but the body looks worse that the already installed one.

 

[HoughMade]

The stock petcock, which yours looks like, should only flow on Pri with the engine off. Yours has something wrong with it, or someone "fixed" it. The absence of a vacuum line should cause it not to flow if the petcock is working as designed.

 

[Snoman6115]

ya mine did the same thing even after i replaced the diaphram and all that. i just bought a small inline shut off switch made by briggs and stratton for lawn mowers and put it in where the line goes to the carbs. works great for me, i just close it before i park it for a while, like overnight and then it doesnt leak from the air filter.

this is basically waht i have
http://www.amazon.com/dp/B0038U3JKM/?tag=hyprod-20&hvadid=15473268099&hvpos=1o5&hvexid=&hvnetw=g&hvrand=7004552761496009936&hvpone=&hvptwo=&hvqmt=&ref=asc_df_B0038U3JKM

 

[nico]

Someone "fixed" mine by making it just an open line pretty much. Removed the spring so when I bought a rebuild kit and rebuilt it, I didn't even know it was missing til my bike wouldn't run. Very frustrating. Save yourself money and hassle and just buy a manual one.

I ordered mine from MikesXS but other stores have them cheaper. The one from Mikes lined up with the holes in my 78 just right but I had to do some "modifying" to the lip on my tank for the Reserve position(bent it with pliers, easy). As soon as I replaced it my bike started. And no leaking!

 

[HoughMade]

I did essentially the same thing, but I cut a groove in the lever so it clears the tank lip.

 

[sly409]

I think I'm gonna go with a manual one as you guys have suggested. Adding an inline shut off just seems like a new step I'd have to remember every time I park my bike and I'm likely to forget it lol.

 

[sly409]

well I know why my petcock is leaking now. spring, diaphram, valve oring, and selector gasket all worn out. I think there is suppose to be a plastic spacer there too but its all gone. Would I be better off spending 40+ for a manual petcock or 15+ for a rebuild kit?

 

[sly409]

can anyone tell me what this plastic looking thing is? mine didnt come with one, just a thin metal pipe that fits into the left hole on top of the petcock. Thanks!

 

[drewpy]

its a fuel filter, and if you are likel to forget to switch off, I'd rebuild it.

mine works great after rebuild

 

[xs400newbie]

its a fuel filter, and if you are likel to forget to switch off, I'd rebuild it.

mine works great after rebuild

It came like that stock? I added an external filter without checking if I had one of those. Would an external one still be needed?

 

[HoughMade]

When I put the manual petcock on, I removed the screen filter inside the tank. I did this because with an inline filter, I wanted the filter outside the tank clogging if anything so I wouldn't have to take the tank off to clear a clog.

 

[drewpy]

I have both, like the advert, double cold filtered for that smooth run