As far as i'm aware the importance is not so much with the ligkage with the pedal, but with the linkage between the carbs them selfs. It is extremly important that the carbs are syncronised to each other so they all draw the same amount of air at idle, failure to do so will cause one cylinder to draw more air and so more fuel and accelerating the engine, this in turn draws more air from the other 3 and adds to the problem. If the linkage between the carbs is poor they will probally fall out of sync. as soon as the trottle is opened, i also had this problem when itinally setting them. Initally i removed the trottle cable , screwed the idle screw out untill it is not in contact with the leaver, then back in untill it just makes contact with the lever then a further 1/2 turn, set the idle mix screws out 2 full turns from fully closed, start engine, using choke if required, and when engine is warm i.e. choke fully closed, adjust only the idle mixture screws to attain a moderate idle, then sync. the carbs to each other with a flow guage, as for the cable i have a top mounted twin cable system but only use one cable, its from a bicycle but works well
Sounds like a little more balancing will help. Ensure the carbs are both drawing the same amount of air (as per jamez), then screw each idle mixture screw fully in (dont force it) one at a time, then screw back out until the best (smoothest) idle is achieved. Each screw should end up around 1, 1-1/2 turns out if the correct idle jets are used. Adjust the idle speed to finish.
