71 cb 750 carb problem

[bradengineer]

Ok, I just bought this bike and am trying to figure everything out on it. I took the carbs apart and cleaned them cause the bike had been sitting in a storage shed for a couple years, they weren't that bad either, just a little sticky. Now the problem, When I let the bike sit over night gas leaks out of the overflows o all of the carbs. There weren't any hoses on the overflows when I bought it and I haven't replaced them yet but it doesn't seem like it would make a difference. Should I shut the gas off on the petcock when I'm not riding the bike? I'm not sure, this being an older bike, if there's something different about the way these work. Or is it probably a problem with the petcock not working right, shutting the gas off when it should? Any help would be great.
Thanks
Brad

[Laminar]

I make a habit out of turn off the gas when I park all of my bikes.

It sounds like you need some new float needles like these:

http://cgi.ebay.com/ebaymotors/CB1100-CB900-CB750-CB650-Carb-Float-Needles_W0QQcmdZViewItemQQhashZitem5887280657QQitemZ380224669271QQptZMotorcyclesQ5fPartsQ5fAccessories

(Make sure those match what you currently have before buying, though)

Also make sure your float height is set correctly.

Not to chase you away, but you'll probably find more specific SOHC help at a place like the SOHC/4 forums.

[NH750Kitch]

+1 on the SOHC/4 Forums, Brad.  It's a wealth of information and expertise for our old fours.  Good Luck.

[Munkey]

How much gas is leaking out?

I started riding bikes back in the 70's and from my experience back then, you had to remember to turn off the petcock or gas would leak out. This is what led to the invention of the vacuum petcocks that we all deal with now.

If it's not an abnormally large amount of gas, then I think it is normal.

[m98]

I echo Munkey on this one, turn the petcock off. Try that before you run down and
buy a bunch of stuff. If I remember correctly, late seventies or early eighties is when
the bikes began to come with the vacuum system so you did not have to shut off the
petcock.

[6pkrunner]

The floats are not completely shutting off the fuel. When the bike is on its sidestand the level is high enough to flow out the overflow .

The floats may be leaking and taking in fuel that weighs them down.

The floats are not free to move on their pin axis. Exaggerated when bike is on sidestand. Binding somewhere between float/pin/carb body.

The float height is incorrect. Easily rectified.
Float height adjustment

The needle valve/seat are contaminated. Clean or replace.

Since you say it happens when the bike sits on the sidestand, I'd try float height/free movement first first.  One or more could be sticking.