Any motorbikey folk in?2002 Aprilia Mille i stalling problem

[robbocop33]

Strange problem with a 2002 Mille v-twin,18k in great condition overall.
Bike starts perfectly everytime from cold,runs spot on,however,sometimes if your pootling along in a 20mph zone it suddenly just won't respond to throttle,it just wants to die,if you keep the revs up and slip the clutch it keeps going,if you pull over and let off throttle it will just stall!
The bike will immediately start up no problem and 'might' still have this wanting to stall problem for a mile or so,then it clears itself and it's fine!!The bike is always perfect at high rev ranges,only does this at 20mph zones.During these wanting to stall times it never stutters violently,just smoothly transitions into not want to respond to throttle at low revs?
I recently had a good look under the tank and noticed cracks in the throttle body mounting rubbers,replaced these,also done plugs,checked hoses,cleared out a blocked tank water drain and cleaned/re-oiled k&n filter,but bike still has this fault,anyone any ideas?
Incidentally once it's showed this fault in a day it never does it again?

[Paul Mann]

The Mille uses a stepper motor controlled idle valve that moves a pitson up and down in a cylindrical housing, opening ports in the side to control the idel air bleed. It's fairely common for these to get stuck with age, the plastic piston swells and gets tight and this can cause stalling. The idle valve is mounted under the airbox.

[robbocop33]

Paul Mann said:

The Mille uses a stepper motor controlled idle valve that moves a pitson up and down in a cylindrical housing, opening ports in the side to control the idel air bleed. It's fairely common for these to get stuck with age, the plastic piston swells and gets tight and this can cause stalling. The idle valve is mounted under the airbox.

Discovered two things yesterday,put the bike in diagnostic mode and tps position on the dash was showing '-1'?Should be '0',also discovered on the right hand side of the throttle bodies there is an inline one way vacuum check valve,out of curiosity i took the check valve off and i was able to blow through it both ways!
Now this check valve i've heard two opinions about,it 'does' have an effect on governing the vacuum to the throttle bodies at idle!which would make sense,then i've heard this check valve only makes the clutch smoother,sort of a slipper clutch effect on the clutch?
Whatever,i rode the bike this morning and it's sweet as a nut!! ;-)