TOPIC:

I have a quick question to ask you. I have just finished rebuilding this bike, and I do not believe everything was hooked right when I started. I am doing work on the carbs now because I am not getting any fuel through them. The question I have is about a three way joint in between 1 & 2 and also in between 3 & 4, I have attached a diagram from the manual that shows a hose leading off of the third leg of this joint but it does not show where it goes. I don’t know that this is the cause of my problem, but can you tell me where it is supposed to go to?

That is your overflow drain. Does not hook up to anything. On mine the hoses run back over the airbox, and will keep gas from dripping on your engine if your float or needle stick.

overflow is usually in the bottom of the bowl thoes are vents that hook to the airbox

Well they may be vents, but I did have a float sticking and that is where gas poured out of until I tapped on the carb. There is no place to connect to hoses to the airbox. The hoses run over and behind it.

They are vents. Please see the BS series carb connection link on my web page.

wiredgeorge - Can you please post the link you are refering to? I may have been looking at the wrong page on your site but I only saw the vacuum ports talked about, which are on the other side of the carbs, and there is one on every carb. these are only between 1/2 and 3/4.

www.wgcarbs.com/101348.html

I explain on that page that some BS34 assemblies have vent tees between the 1&2 and 3&4 carburetors and some do not. Some vent via the large slot on the venturi edge on the airbox side. Some vent via the tees.

Wow are those BS carbs? Those look just like my Keihen carbs on my 83. Except I only have that T in between 1,2 and 3,4. There is no fitting to attatch them to the airbox. I looked at the parts diagram for mine and they are labeled air vents, so you all were right. But I did have gas come out of one once when I had a fload stick. So that made me assume it was an overflow. You know what they say about assuming.

It connects to fittings on the valve cover not the air box.

cnyl... The tee fittings are vent tubes. They do not connect to the valve cover. The valve cover fittings are emissions control reed valve openings. These are connected to the airbox and to a vacuum operated valve. The vacuum operated valve connects via vacuum line to the #1 and #4 vacuum ports on the engine side near the mixture screw through a tee fitting. If the emissions stuff is missing, the vacuum ports must be capped with vacuum caps. The #3 vacuum port will have a cap from the factory as it is only used to sync carbs and the #2 vacuum port is attached to the petcock via vacuum line.

Travis, The BS carbs pictured may look like Keihin CV34s to you but that is because they function similarly and will have the same outward charcteristics as a result. The Hitachi and Tekei constant velocity carbs also look "similar". Note in the drawing that the Mikunis have choke plungers rather than using choke butterfly valves on your Keihins. The bowls are shaped differently as well... the bowl gasket on the BS carb is rectangular while the Keihin CV is shaped like a house (can't think of a better way to describe the difference). The other main difference is the Keihin uses a transitional jet system to aid midrange which they call a "MAIN JET" and they also use a "SECONDARY MAIN JET" which is actually the main jet. The main jet aids the jet needle in mid range to meter gas on the Keihin while the Mikuni BS relies on just the jet needle.

its possible that the vent hoses don't connect to the airbox - mine don't.