Carb SyncronizationThe purpose of syncing the carbs is to create an even balance of fuel mixture going to each cylinder. This is achived by adjusting the amount of throttle opening on each carb to produce an equal amount of vacume for each carb.
The carbs are connected by a sync rod having threads at each end, a locknut on one end, and flat sections in the middle to turn the rod.
Vacume is measured either with the use of mercury manometer (fig 1) or you can construct a homemade syncronizer using a vacume guage and a few other redily avallble items as described later on.
To have the bike shop sync your carbs will cost around $40.00, the cost of a manometer is also about $40.00, but you can re-sync your carbs later on for free.
It only takes a very small amount of mercury to contaminate a drinking water supply, so please use extreme care when handling a manometer.
You will be taping vacume off one fitting on each of the intakes, so while the bike is cold, decide which two fittings you will use and take them off and put them back on . You will be removing them when the bike is warmed up so you want to make that easier.
Place the bike on a level surface on the center stand and warm the bike up to operating temperature. It is advisable to have a full tank of gas.
Shut off the engine and remove the two vacuum lines or caps that you previously loosened. connect the manometer or vacume guage setup to the fittings (the manometer will come with instructions) Loosten the locknut on the sync rod while holding the rod from turning with small vice grips or pliers. Tighten the locknut finger tight.
Start the bike and note the readings for each cylnder, The goal here is to make the readings as similar as possable. This does not particularly mean that you will have the highest readings possable, you want them as CLOSE as possable.
Loosen the locnut and slowly rotate the sync rod until the readings match up. You will have better accuracy with the manometer than the vacume guages, but they should still provide satisfactory results. expect your ilde speed to change.
When your readings match, hold the rod from turning and carefully tighten the locknut enought to keep the rod from turning, but do not overtighten, those threads are thin and will strip out if you apply too much force. Adjust the idle speed as required . double check the readings to be sure they are still matched up.
Remove the guages, reconnect your hoses and go for a test ride.
If all goes well you should be rewarded with a smoother, cooler running, more responsiv and easier starting engine.