71 Commando 750 starting fine, IDLING HIGH

Hi,

My '71 750 has been sitting for over a year, ever since my original fiberglass tank corroded and started leaking around the petcocks (past the point of rebuilding). When it was running, my only other issue seemed to be a sticky throttle. Mostly coming to a stop, neutral, or 1st to 2nd, it seemed to continue to accelerate. Mikuni 34mm carb has been cleaned and examined numerous times and the needle doesn't seem to be sticking. Throttle cable looks alright. I was going to try the SECOND spring trick in the carb, but never got around to it (remember the leaking gas tank?).

Fast forward to today.
Got a new (old, but perfect condition) tank. I can get the bike started pretty easily. I have never really needed choke, or very little just to get started. But as I get started, the idle starts running away...up to 7000+ rpms, and will rock off the center stand. So, I quickly turn the idle screw WAY OUT to get it down....and it does come down to a reasonable idle at like 8 TURNS OUT, where it's about to fall out of the carb. Obviously this is not right.

Granted, I may have THOUGHT my problem last year was with a sticking throttle, and really it was just the same symptoms of this runaway idle.

Quick diagnosis of the key things that may cause this?

thanks

Pretty rare if not impossible for Miki slide to slick up foo redline idle. Air leaks are first to mind of course then worn slide letting air flow past but you've likely nipped that up so first thing I'd look at is spark timing if point system. Don't guess ya forgot which way the enricher level functions. Might try to grease slide for temporary test of slide fit air leaks as will soon wash out into engine burning. If electro ignition and good voltage then a real mystery.

Pull the air cleaner and see where the slide is and see how the throttle screw effects iy visually and by finger feel.

You have been fiddling with this carb a bit. The needle is soft and can bend easily. I slight deflection, unseen by the eye, will cause a drag in the needle jet. While you have the aircleaner off check for drag here. If need be, pull the needle and roll on flat surface. Tweak till true.

Make sure your idle screw and your mixture screw aren't mixed up. Don't take offece here, just trying to cover the bases as you explained the game.

Make sure your throttle cable isn't adjusted out all the way. Just as a way of ruling it out, slaken the cable all the way off. I had a similar issue until I realized my cable was a tiny bit tight.

Simple thing to check.

Ben