Topic: Air Vent tube from Air Cleaner Housing

[Williamsd]

This is a question about a 1982 CB650SC.  In the attached diagram you have an air vent tube (part #8) that connects to the Air Filter Housing (part #5) at the bottom right spigot (close to the #28).  Where does the other end connect to?  I'd swear that this was disconnected  when I got the bike so I assumed it was just a drain.  I was trying to figure out whether it needed a plug like part #15 but when you look at this diagram it suggests something else.  Any ideas?   

[82CB650SC]

If I remember that hose connects to the tee that vents carb 1&2 and 3&4
the tee is part #20

[DrMark]

If its the bigger 1/2 inch size hose...it might go to the oil breather on top. Is its the smaller ?3/8 in hose, it might be the gas scavenger hose from the carbs.

[Williamsd]

Okay... we are making a little progress here.   

I bought an engine and carbs last fall in New York State and just completed the engine swap (using my original carbs).  My bike is of Canadian origin so the original carbs are different from the US carbs that I just bought.  Question is how much different?  The US set has the connector parts (10,11 & 20) shown in the attached diagram.  There is however no evidence of any scavenger tubes on my original set.  I can't get in to see if the holes are even drilled out of the carb body.

Was this scavenger system used on all CV carb models?
Anyone know if this would effect the performance if the scavenger system is actually missing? 

[byidesign]

On my {u.s. version} 82 cb650sc there are two "T" fittings between carb one and two ,just behind
  the butterfly pivot down between the carbs, the same for carbs three and four. they have @ 8inch length of tube,and come up to another "T' that is on top of the airbox{very top} right under
    where the seat fastening bolt goes. this goes into a fitting into the airbox. the large 1/2 tube
      goes from the middle valve cover to the right side top of the airbox.
         hope it helps

[Williamsd]

Thanks for your help.

I talked for some time with people at the local dealership (both parts and service) and this plumbing is supposed to be on the Canadian model as well.  The mechanic said it is just connected to the float bowl vents and so long as the vents are not blocked it wouldn't be a problem.  Since the carbs are such a pain to get in and out I guess it is going to stay that way.