Hi there,
usually swelling of the rubber is caused by alcohol, and leaving it out in the (warm) fresh air reverts the process. If it shrunk, you can get it to original size again by dipping it into methylated spirit.
The carb is not to be synchronized, so there is no tool for that. Syncing carbs is done with on multicylinder engines with identical carbs supplying their individual cylinders.
The XT carb is a 2-stage- carburettor, where the primary carb (left) is actuated via throttle grip and slider, while the secondary (right) carb opens around 3500-4000 rpm (under load, so NOT when revving the enging) to assist the primary carb. The secondary carb is actuated via vacuum, which is initiated by opening a butterfly valve, which then causes the pressure difference to suck on the diaphragm and lift the slider. Also check the condition of the long vacuum line connecting both carbs. Slide should run smoothly inside its bore when pushed.
The starting point of that opening of the throttle (butterfly) valve can be modified with a set screw, and the default for that is when the primary carb slider opening approaches a set value (different per model). For 1VJ and 3AJ this is 7 mm, for 34L or 55W it is 5 mm. As with the idle mixture setting, this is a safe starting point, but the correct setting for the secific engine should be tuned to fit engine condition, altitude etc., so I would recommend to change the setting half-turn wise and do test rides with various settings.
The starting value is easiest set by inserting a e.g. 7 mm steel rod (aka spiral drill bit) under the slider, then turning the set screw so the butterfly juuust begins to move.
You can leave the carb in the bike when adjusting, only the air filter rubber boots have to come off.
Check the exploded view (open in new window):
https://www.xt600.de/xt_werkstatt/_spec ... losion.htm
(34) vacuum hose
(45) set screw
Andy
