1999 EV Throttle Bodies

[1Sourdough]

Some weeks back we chatted about the rough running my EV was doing.  I synched the TBs, and everything was sweetness & light.  So an area rider suggested 1 1/2 turns out on each air-bleed screw might be a bit excessive, so I turned both in 1/2 turn, to one full turn open.  A few days ago I noticed the engine seemed to 'bang' on one cylinder, and was backfiring lustily on deceleration.

This morning I checked the air-bleed screws, and found they were both 1/2 turn from closed.  Turning both out an additional 1/2 turn brought much smoother running, and a reduction, though not elimination, of backfiring on decel.

I will accept the possibility I cannot count two half turns of the screwdriver, and only had the screws open 1/2 turn but I thought that screw was only supposed to affect idle.  Why is it making a big difference at 3000 and higher RPM?

These are the throttle bodies which have only one mixture adjustment, the screw which hides up inside a shroud on the side of the unit.  Any thoughts?

[Kiwi_Roy]

It's not really a mixture screw it's a bypass around the butterfly used for fine tuning the idle and throttle balance at idle.
It will have a very tiny effect on mixture because at 1-1/2 turns rather than 1/2 turn the throttle is slightly less open to get idle speed so the TPS mV
is a few mV less.