Here's a quick and reliable way to install vacuum ports on your bike if your carbs don't have them. My vm29s don't and I want to ensure good balance. Ensuring good balance between carbs has made a big difference in ride quality and performance on many of my other bikes and it's bothered me that I've never had a way to check these.
I bought 5 mm threaded vacuum ports to install in the rubber boot. Other places to add vacuum ports are on the carb body, behind the slide of course, or on the cylinder head by tapping into the intake port. There is no room on the vm29 carb and the head of a cb750 requires removal of cooling fins on the out cylinders to make a good spot. I don't want to do anymore work on the cylinder head so to the boots it goes.
This is easy enough. Just drill a hole in the boot the same size, or close, to the minor diameter of the threads on the vacuum port. Clean off the debris nd test fit the port. Add some gasket maker to the threads and screw them into the boot. Let them dry and cap them with the supplied acuum plug. Done and done.
Now you can go back to the precious article and vacuum sync your carbs. Woohoo!!!!!
Vacuum port with gasket and sealant.
Installed. Maybe a little tacky looking, but with the rubber caps and the carbs back on I dont think they'll be very noticeable.
