i need help on how to fine tune my carbs. i just finish cleaning all my carbs. i have all the air /fuel screw trun out to the same (about 2 1/4 truns out) that's what it was when i started. i got everything back together and took her out for a spin. idle is fine, but when i open her up. she has a flat spot till about 5 to 6,000 r.p.m ,then she runs like a champ. i though on my carb sync gauge and carb 1,2,and 3 are at 200kg and # 4 carb is at 150 kg. would that cause my low rpm flat spot?
and to get carb 4 up to 200kg do i adj the air /fuel screw or the butterfly?

 

For carburetor synchronization, you should get the valves at least checked because they determine ultimate air-flow through the engine. The Air/Fuel screw or pilot screw as it is referred to is only for adjusting the mixture, not balance. It can affect engine RPM as you adjust the mixture, but not balance. There are 3 screws for adjusting the carburetor sync. Everything is done in pairs. The actual amount of vacuum you're reading doesn't matter so long as they are equal. Use the screw that is between carbs 3 and 4 to get them balanced with each other. Then adjust carbs 1 and 2 to each other. The screw between carbs 2 and 3 is used to then bring the 2 pairs of carburetors in sync with each other.

 

J