Carb Sync Help

my bike has screws in some of the ports that aren't being used. They are right below the rubber boots that connect the carbs to the cylinder head. Two of the ports have vaccuum ports screwed into them; one is connected to california emissions crap, and the other was for (a now nonexistant) vacuum shutoff for the fuel tank. Someone may have screwed in vacuum ports into yours for balancing and then put rubber boots to cap them off?

 

I'm thinking you might have that backwards??

You can do a bench sync with the carbs out to get them "close" but the engine must be running with vacuum guages on each cylinder to dial it in perfectly. What you are doing is matching each of the carb butterfly valves by measuring vacuum behind them. If one butterfly is just a miniscule amount different from another, there will be a difference in vacuum behind it.

 

Sorry to take this further away from the OP, but since it's still related to balancing, I'll say this:

Since you've attempted balancing and don't sound happy with it, I'll suggest you check a few other things. Balancing is real easy and the butterflies are either matched or not. It's all there on the guage and it's just that simple.

But, because the butterflies are matched, it doesn't mean the motor is running balanced. In theory - you could have a cylinder that's not even running and still "balance the carbs"

However, there are other factors that go into getting the engine to run balanced. The first would be having the valve gap matched and even along with the condition of the cam lobes. Second would be float levels in the carbs being set properly. Third could be a partially blocked jet and 4th could be the needle/seat screen. There are probably other things that could be added to the list. My point is that the "balancing" of the carb with the gauge is the last of all.