Mikuni BS34 Carb overflow question

[Dennis Moore]

Greeting all. I have Mikuni BS34 carbs on my 1982 Yamaha Seca XS400RJ that don't have an external over flow tube. I don't see anywhere that it would be connected on the carb bodies. I had an overflow incident recently and the air filter was pretty much drenched. Is this typically where the overflow drains as opposed to through a tube? Thanks.

Dennis

 

[amc49]

The overflow is usually in the bottom float bowl. Comes out the bottom when it happens, a really bad case has that tube overwhelmed and then it comes out the top needle jet to go into engine.

 

[xschris]

These carbs are not equipped with over flow tubes. If they do over flow they will leak fuel out of the bowl vent holes on the front to the carbs. This usually happens when the float valves go bad or the petcock don't shut off as it should. Sometimes the with brass floats they get holes in them causing them to sink.

 

[amc49]

Ethanol laced fuel will do it if the bike sits several days, the fuel dries up in bowl much faster and then the residue left behind sticks the float needles at wherever they are at. I have utter fits with it on my Honda CB550F. I had to develop a quick procedure to unstick them every time I wanted to ride the bike. Unstuck and liquid fuel present they go back to working perfectly until the carb bowl begins to dry up again.

 

[Dennis Moore]

These carbs are not equipped with over flow tubes. If they do over flow they will leak fuel out of the bowl vent holes on the front to the carbs. This usually happens when the float valves go bad or the petcock don't shut off as it should. Sometimes the with brass floats they get holes in them causing them to sink.

Thanks, XSChris. I got the same info from another source. I've ordered a rebuild kit. I was just curious as to how the overflow works.

 

[Dennis Moore]

The overflow is usually in the bottom float bowl. Comes out the bottom when it happens, a really bad case has that tube overwhelmed and then it comes out the top needle jet to go into engine.

Thanks, amc49. Oddly these carbs do not have an overflow port on the bowl.

 

[amc49]

I have since found that out. Never stop learning.