recommend you FIRSTLY check 1) engine compression 2) timing 3) valve clearances.
First you have to be sure you have the essentials right. Otherwise you are on a hiding to nothing, no amount of fiddling with carbs will get it right.
If all above is OK, remove dashpot chambers & pistons & check for wear. Do the "vacuum" check as per Vizard. Then check throttle butterflies for synchronisation. Check for excessive wear in the spindles. You can get away with a little play here. Check the springs in the vaccum chambers to see if they are the same length. lastly, check for air leaks, make sure gaskets are all ok and smear with a little gasket goo-just a fine smear not like your'e icing a cake! Also, check the mating faces for the manifold to make sure they are flat. I like to true them up by using wet n dry and a flat pane of glass. Obviously, this means fully dismantling the carbs and checking everything, but nothing here is beyond the average person's ability.
One last thing, check for air leaks wear at the manifold/head. The gasket should be renewed and the mating faces of the manifold should be trued up as above if necessary.
Enough info here for 100 thread counts.
), but I hear a lot of SU problems can be not enough dashpot oil, or the wrong type. check the obvious above as people have said plus don't forget the dashpots.
