Mikuni carb nightmare

[alankusov]

I've just put together a 65 Suzuki T20 two stroke 2 cylinder and have major issues with the original Mikuni 24 VM carbs. It idled fine until one slide valve used to get stuck open. To remedy the issue, I took the carbs apart, cleaned them thoroughly and polished the valves & chamber. Bike started up fine with small adjustments of the valve height adjustment and air screw. Still not sure if the cylinder valve needs to be fully closed or how high it needs to be for idle.
The really problem was when I gave full throttle the engine would either come down to idle way too slow or even worse...get stuck in high rev (strong rev). I only had 4 strokes prior to this and don't know if this slow return to idle is normal for 2 strokes. Anyway at that point I could only turn the ignition off. To my horror, in one instance when it got stuck in high rev, it started to diesel by itself. I panicked, pulled the ignition key out and disconnected the ignition wires...it still dieseled. It only died when I opened up the choke few seconds later.
I suspect that either the valve is still sticking or I have a leaking intake manifold. The cable is new and well oiled. Does anyone have two cents on this one? I appreciate

[gregorious77]

sounds like its running very lean.

[dekker]

Does each carb have a choke or is it a single choke.... I know sometimes a dual carb set up will have one choke and a tube that runs between the two carbs to bring fuel to the other one for choking purposes if that small piece of tube is not between the carbs it can cause over rev symptoms where it will not come back down.