carb balancing

[gearhead65]

I set up my vacuum gauge to check the vacuum on my carbs, but when I started the bike, the needle on the gauge was so erratic, I couldn't tell what it was pointing at. I was using the regular automotive type vacuum gauge. Is this the right one to use? I have never heard of one that is motorcycle specific.

[BuzZz]

Sounds like your set-up is too direct. Whatever hose or line you have connecting the gauge and the carb needs either a restriction (orifice of some kind... a needle valve works well) or more volume in the hose to allow for the air within the hose to absorb some of the pulsations caused by the intake pulses. Softer type hose helps here too.... rubber instead of braided steel for example.

Try that and see if it helps smooth the readings out.

[jimharvey1]

Yeah...a valve to restrict the size of the opening will better "average" the high and low sides of the vacuum. Nothing fancy. You can actually go to Walmart and pick up a 4-way gang valve for an aquarium set up and use it. Hook all four hoses from the valve to the carb venturis and the gauge to the open end. Start the bike and open the valves one at a time closing them just enough to get an "average" (stabilized) reading. Used it on the Honda 550 I had and it worked like a champ.