I replaced the stock Mikuni with a Weber 32/36, and there's a thread on here somewhere with more details. But one thing you might have to do is add a return spring, to make sure the idle arm fully returns.

When I first installed the Weber, I followed the instructions to adjust the fuel/air screw (basically turn it in until the engine almost dies, then back it out a quarter turn at a time until the engine starts to run rough, then turn it back a quarter to half turn). Once that's done, setting the idle screw is pretty easy, but the Weber is very sensitive to where you set the idle. Don't go any higher than 700-750 rpms, which is lower than the factory recommended setting of 800, and mine actually likes the 600 rpm range.

After I set the fuel/air and idle set screws, I found that the carb wasn't fully "closing" which was resulting in my idle staying around 1000 rpms, and dieseling when I turned it off. When it was idling high, I'd tap the gas pedal, and it would drop to where I had set it originally. After looking at how the carb was operating, I figured I'd add a return spring to "help" the idle fully close, and it's run fine ever since.

I posted some pics in one of the Weber carb threads about this spring that I installed, so I'd do a search and see if you can find it.

http://www.4x4wire.com/forums/showf...;amp;page=0&fpart=4&vc=1

Good luck!