What’s the point of an Vacuum Octopus?

[Hawkinspickle]

Hi folks, I know I have asked similar questions re petcocks awhile back, but I just thought of another one. My ’79 SF had the Octy removed and was running on straight gravity feed petcocks, i.e., just fuel connections. I have a pair of nice new vacuum operated petcocks that I was hoping to use but was wondering if I can run them both each with their own direct connection to manifold vacuum with no Octy? I know there are some posts that describe how these types of petcocks can be converted to bypass the vacuum, but was wondering if this more simple approach might work? In other words, what’s the point of the Vacuum Octopus if the answer is yes?

[bikerphil]

The point of the Octy is it's a fuel shutoff for the Special model where there was limited room for vacuum petcocks. The Standard model has a wider tank where there is room for the vacuum petcocks so no Octy.

Yes you can run aftermarket vacuum petcocks without the Octy on your Special tank provided there is enough room for them.

If you're running pod type air filters there should be plenty of room, just not with the factory airbox.

[Hawkinspickle]

Great explanation. Thank you Bikerphil. I didn't understand that the octy served essentially as a satellite vacuum system due to under tank room constraints. The vacuum petcocks I sourced have a left and right configuration for the fuel line connections that are also at an off angle to allow forward fuel line connections away from the stock air box. I just wasn’t sure if I could go directly into the manifold vacuum ports. Thanks.

[bikerphil]

Yes sir, you're welcome.

[oldyam80sg]

I have Pingel petcocks instead of the stock petcocks. The stock ones are in a box in my apartment. I long eliminated the octy, but still have it laying around. I previously used a Pingel vacuum valve but they can go bad also and must be rebuilt. It was not cheap, and after every ride I shut off my fuel. The Pingel vacuum valve has 2 lines and a tube to hook up to engine vacuum.

[Hawkinspickle]

Does anyone know where I can source reliable 'non vacuum petcocks' (right and left) that will fit the Special bolt pattern? I seem to be having trouble locating one on the interweb. Plenty of vacuum and Standard bolt pattern ones around. I believe the Special has a 34mm bolt spacing. To use a Pingel, I think you have to use an adaptor for their petcocks and they're pretty pricey. Thanks.
Dan

[bikerphil]

Ebay ....

https://www.ebay.com/itm/35427971122...Bk9SR87M7t_0YA

[Hydroman]

I prefer the OEM vacuum shut-off petcocks, but the previous owner had replaced both petcocks. They are not the right ones and both are different from one another and I don't know what bike they came off of, so I don't know which rebuild kit to get for them.

I ended up putting on dual Pingle's with the adapter blocks. I had to open up the holes in the tank, because factory holes were not big enough for the pingle screen to go through. I hated to do this, but I did it. Buying two Pingles and adapter blocks was not cheap.

I don't like having to turn the gas on and off manually. I have a hard time remembering to do it.

[Hawkinspickle]

I was going to do the Pingle swap as well but instead sourced two off of an XJ11 that Bikerphil pointed me to. I heard so much about failing vacuum petcocks and the issue of fuel getting into the crankcase I doubt I'll ever forget to turn then off! That said, it looks like there's other ways fuel might get into your crankcase; see my recent post "The Big Day!".