I have a 1990 CBR600F Cali Model that I have gotten to run (once I cleaned the carbs and turned the pilot screws 2 1/2 turns out) but I noticed that the vacuum pistons do not move at all and I am revving the engine to 4,000rpm.

I have disconnected and plugged ALL the vacuum line ports on the 4 separate carburetors. I am assuming at this point that I need to put vacuum lines on some of the carb ports to get the vacuum pistons to work? I am trying though to remove as much of the emissions as possible.

Thank you in advance for any and all help.

 

This is a picture of one of the ports (carb #1) that I have plugged. We go the motor running after turning the pilot screws out 2 1/2 turns. It seems to run fairly well, but the vacuum pistons are not moving at all. They are staying fully inside the throat of all 4 carburetors.
Thanks in advance for any and all suggestions/help.

 

They need a load to move more than slight flutters if free revving. If they are bouncing up and down slightly while free revving you are probably fine, if it is running fine otherwise. The vacuum system for the pistons actuation is internal to the carbs. That exterior port has nothing to do with it.

 

Thank you drakito!

I was assuming all the ports on the outside of the carbs did not operate the vacuum piston. Thank you for confirming that these outside ports do not.

I will have to pull off the air cleaner and rev the motor and watch for flutter of the vacuum pistons. Is there an rpm range that the vacuum pistons would start to flutter while free revving?

Thank you very much again!

 

As soon as you throttle on you should see them start bouncing. There are 2 vacuum ports internally to actuate them. The first is in the vacuum cylinder itself and it bleeds directly into the carb's main bore. The second is integral to the metal cap on the top and it is a tiny little hole that feeds to some of the airbleed lines in the carb body.