hi. im having a problem with a small cox motor. i can start it fine, and it runs fine at high speeds, but when i try to idle it the motor dies. i cant seem to find a low speed needle on the motor. there is a small screw next to the high speed needle, but it doesnt seem to have much of an effect. any advice on how to control the idleing of the motor, or if there even is a low speed needle to adjust? thanks!