The issue - At first, he bike takes forever to start, regardless of how much (or how little) choke I apply. The bike starts eventually, but the idle is all over the place. Giving any throttle blips only spike the rpms up high where they hang for 2 secs or more, and eventually go down.

The only way the bike will rev up and down freely and ride smoothly is if I completely loosen the idle speed adjusting screw. Obviously, the bike dies when I stop, because the idle speed with no adjustment is too low to maintain the bike on.

Valves were adjusted, carbs were cleaned and synced, and spark plugs were replaceds as well. Fuel mixture screws were set to the factory 2.5 to 3 turns. On that note, the problem remains whether the fuel mixture screws are 3 turns out, or as high as 7 turns out, and it makes no difference whatsoever, so I know that the problem is NOT the fuel mixture screws.

So what could be causing my bike's erratic idle and sticking RPMs? A friend of mine told me that it could be warped or broken carb diaphragms, or something as simple (however unlikely) as a stripped/stretched throttle cable.

Thanks!!