how to syncronize carbs on 1980 honda cb 900c?

Answer 1

I had a CB750 that I rode for years.
For Synchronizing the carbs I had a set of 4 vacuum gauges that had flexible tubes that connected to the vacuum port on each carb.

Start the engine and adjust the carbs until the vacuum readings were all the same first at idle then at 3-4000 rpm.

Before the gauge set I had a set of 4 glass tubes 1/4" in diameter, about 36" long. The glass tubes were in a sealed common mercury reservoir at the bottom. The tops of the tubes had long pieces of surgical tube that I connected to the carbs. you adjusted the carbs until the mercury in all for tubes was at the same level. I actually liked that set up better than the gauges. But one of my boys broke the tubes. Gauges are not as vulnerable.


For what it's worth:
Yours:Grumpy

Answer 2

Grumpy is spot on.... one additional detail, make sure the carbs all lift together as you open the throttle.. using the same gauges make sure they all raise and fall together.