Topic: Auto/vacuum-actuated petcock in cb550 '76?

[kippstakes]

I was pondering whether or not the vacuum petcock on my gsxr 600 was working properly today, which led to me pondering how annoying it is to have to turn my cb550's non-auto petcock on/off every time I ride.. and when I forget to switch it off, well, it doesn't end well sometimes (turns out carb needles aren't flawless gizmos). I think you can guess what this train of thought led to.
Has anyone had luck installing a auto petcock on a cb550 tank? The vacuum source is easy enough- just buy a 5mm nipple and pop it into one of the manifold sync ports. I guess the stumbling block would be 1. finding an auto petcock that could deliver fuel at the same/greater volume as the original grav feed, and 2. either finding a petcock that has a bolt that would fit the tank's threads or a petcock you could install as an inline system.
There are a million petcocks out there, it seems like one should fit the bill. The cbr600's seems like a possibility. I have also seen inline versions for scooters, but I'm not confident that they would generate adequate fuel flow.. but maybe?

Any ideas, suggestions, experiences, successes??
Thanks

[mrfish2]

In my opinion you wouldn't have enough room under the tank to run a vacuum peacock in-line with the fuel hoses, and the fact that there are 2 hoses under there makes it a bit more complicated as well. I'm not fully versed in the inner workings of a modern petcock but it doesn't seem that one made for a modern bike would work well for a vintage bike.

If i were you I'd just start remembering to turn the petcock off every time you get done riding   

[Deltarider]

And in my opinion you would miss the occasions something is wrong with the floatneedles...

[Gordon]

The CB650C has a factory, in-line vacuum switch for the petcock, so I'm sure you could use one of those if you can find one.  I doubt you would run into fuel flow issues using an in-line one intended for a scooter.  The vacuum switch doesn't really regulate how much fuel can flow, it just turns the flow on and off.  The issue you'll have running an in-line switch is that your stock petcock doesn't have a "Prime" position, so if the bowls have run low you'll have to create vacuum either with the starter motor or by kicking it over for a while until they have filled up enough for the engine to run.

You could check to see if the 650C petcock will fit your tank, but I'd be surprised if it does.  Petcocks are one of those things they seemed to redesign for every model and even different years of the same model.     

[strynboen]

think one from Yamaha dt 125 can be used..just put the vaccum line on one of the vacum cyncro plugs

[vames]

what if you were to leave your stock petcock but install a small vacuum-operated on/off valve in the fuel line. I thought about doing this a long time ago but I just learned to turn the petcock on and off as part of my start/park procedures.

http://www.amazon.com/Valve-Vacuum-Petcock-Scooter-Moped/dp/B00D7N8HRK

[kippstakes]

Thank you for the quick responses. I have found a few inline petcocks that should work, and the nighthawk petcock seems iffy as far as mounting goes- they are, however, not expensive. The priming problem had crossed my mind also. I thought about the possibility of installing one line with a manual petcock, and another with the inline auto, but it seems almost as easy to just remember to turn the one I have now off.
I guess I'm on the fence at the moment.

[strynboen]

 some (not all)Yamaha /Suzuki have primer build inn.. normal is....op is prime... mittel is run/auto off..and Down is reserve..