vacum plug

[Parr8hed]

This is probably a stupid question, but here goes. Driving to work last night kinda rough idle, backfires alot during downshifts, notice a weird hissing sound every so often down by the right leg. #4 carb has a vacum port that is open. I thought that was plugged off? cover it up with my thumb (while riding) bike runs much better. Idles great. If I could have gone down the expressway at 70 with my toe over the port would have been fine!! I got a needle cap (hypodermic, not carb needle jet) and covered the opening. bike rode great and behaved all the way home, even in 42 degree temp.

Is this port supposed to be plugged? I thinks so, but just making sure.

Thanks.

[xssiveone]

#4 carb has a vacum port that is open

#4 carb, or #4 carb joint? #2 carb is the only one that has a port actually on the carb and that is connected to the advance unit. The rest have ports on the intake rubbers or carb joints. In any event, yes, they should be covered. 2 have to be connected to the petcocks, the others should have caps. They get dry and cracked so it's not impossible to lose one. Any automotive store should have a suitable replacement. Or, get a small piece of hose and put a screw or plug in one end. Doesn't look pretty but it will do until you can find something better.

[Parr8hed]

yes it is the carb boot/joint whatever that thing is called. i will get a proper replacement today. thanks for the info.

[John]

I believe it will use a 3/16" vacuum cap.