SUs are the most simple carb in the world... once you understand how they work - only prob is not many people do!

Seriously, there's not much to rebuild. If they don't flood (sunk float or needle and seat probs) or leak fuel, you really don't need to 'rebuild' them. SUs don't have accellerator pumps that wear like conventional carbs, or power valves or anything.

*Strip, inspect and clean the piston chambers.
*Check that the needles are 'shouldered' in the piston - ie the shoulder of the needle should be level with the base of the piston.
*Check that the jet is centered.
*Check condition of the springs (ie not bent or stretched, and make sure they are the same - I've seen a few cases where they're weren't)
*Refill the piston damper with oil (about 2/3rds of the way). trans fluid or machine oil works well.
*Set the float levels
*Balance them, and get the mixtures right and you're all set.

That might sound like alot of work, but it's all very simple and quick. The workshop manuals have some good info about tuning SUs, and the usual exploded diagrams etc. They're a good resource when you're learning about them.

One common problem I've seen is people often connect the vents in the float chambers to each other via a hose - not a good idea. It has to be vented to atmosphere. Air cleaner is the ideal place, but if you have ram tubes you can just leave them open.

Its a myth (or common misconception at least) that SUs go out of tune all the time. You'll invariably find that it's only people who know nothing about them that say that. But its surprising how many mechanics know nothing about them as well...They are a good carb for a street car.