Some reading:

http://www.thecarburetorshop.com/Multiplecarburetion.htm

http://www.thecarburetorshop.com/Tripowertuning.htm

http://www.thecarburetorshop.com/Aftermarkettripowersetups.htm

When installing/initial tuning of a tripower; ALWAYS put block-off plates under the front and rear carbs. Once you get the center dialed in, introduce the ends, one at a time.

Jon.

Good carburetion is fuelish hot air
The most expensive carburetor is the wrong one you attempt to modify.
If you truly believe "one size fits all," try walking a mile in your spouse's shoes!
The Carburetor Shop