Fast idle solenoid

How would a faulty fast idle solenoid cause my YBR 125 to keep cutting out when sat idle?

I`m still trying to work out my problem with my YBR 125 before i have to finally take it to the main dealer at £35 an hour and a £60 diagnostics check!!!

I think a fault with my fast idle solenoid, or the sensor related to that has caused my bike to keep cutting out. When the engine is cold it starts up fine...... then as soon as it gets warm it custs out and will not start. I`ve checked everything and i think it`s the fast idle solenoid.

But as a complete novice, i`m not even that sure of the function of the fast idle solenoid!!

My problem can`t be cured by adjusting the idle speed, the spark is fine, the air filter is clean. Not sure what else to check?

when i first start the bike on a cold engine it`s fine, totally normal. This makes me think it`s a small fault.

Help!!