Vacuum/idle question

[Raven91]

I have a bike that I have been working on and I just got it started.  However, it idles at about 4000 rpm, which sounds like a pretty common issue here. I didn't really let it run all that long because it is inside our house, and It started lightly smoking after a few start ups, but I am pretty sure that it is just oil residue from the oil change I did.
My question is about the petcock vacuum port. I attached the line between the petcock and the horizontal vacuum port (looked on the carb sticky thread) on one carb body, but the port on the other carb has nothing on it. Should this have a cap on it, and could that be causing my high idle speed with vacuum issues and such? I know that there are a number of other things that could cause this idle issue, but I havn't had time to work on it recently and wanted to see what you guys thought. Also, is it normal for a bike to smoke if there is oil residue? it wasn't much, but it was enough to be nervous as I am new to working on bikes. I wiped off as much of the old oil as I could at the time, but there is definitely residue left over.

[bmf]

Yeah it should be capped. Oil on head, cylinder fins, exhaust , will all make smoke.

[ragecage23]

I'm having the same problem with my bike. Could I fashion a cap? Or does the OEM cap have something special to it? (Sorry to hijack)

[bmf]

Any cap is fine, you just want to stop air being sucked in, which in turn sucks in gas which in turn ups the revs, unevenly, as it's only on one cylinder.

[Raven91]

I had a leftover length of tubing that I used for the vacuum connection from the carb to the petcock. I just melted the end together to make it air tight and tested it out. It works pretty well now. I can get it to idle consistantly at about 1500 rpm.

Thanks for the advise.

[ragecage23]

I think I'm going to have to try that.