When tuning twins, it is very easy to get it wrong.
You will need to tune the first engine at temp, then switch it off, and fire up the second engine and bring it up to the same temp as the first. Do not fall into the trap of trying to tune both engines at once! If this is not done, I can guarantee that the second engine started will be leaned out too much to match the first engine due to it not being at the same temp, and when running on the track, the second engine will be too lean and may even blow a rod or worse!
You must tune one engine at a time, and allow the second engine to reach the same temp as the first before making ANY needle adjustments. This necessitates the use of a temp gun, and once both are tuned and running on the track, any adjustment made to one MUST be made to the other.
Some problems may be encountered if you use a single tank to feed both engines. Sometimes a lean condition may be caused in one engine due to vibration, this causes a fluctuation in the intake and disrupts the air flow, leaning out that carb, and a single tank can cause this to be doubly worse. The best setup is with 2 tanks that feed each engine separately and use the pipe pressure of the same engine for each tank.
Another simple fix for this condition is to use a smaller venturi, which increases the pulse across the fuel outlet dragging more fuel into the engine.
Cheers.
