Bosch Evolution 300 Series Service Manual page 31

Surface Burner Flame Adjustment
Photo A
A properly operating burner will have clean blue flames with no yellow
tipping, excessive noise or lifting away from the burner head. Photo A
illustrates a typical flame at high setting.
Yellow flames indicate improper fueltoair ratio and can be caused by
improper gas pressure, improper conversion for use with LP gas or
contaminated fuel supply.
At the lowest setting the flame should extend slightly above the burner
cap and approximately 5/8" outward from the side of the burner as seen
in the Lllustration at right.
Test to verify if "LOW" setting should be adjusted
a. Push in and turn control to LITE until burner ignites.
b. Push in and quickly turn knob to LOWEST POSITION.
c. If burner goes out, reset control to OFF.
d. Remove the surface burner control knob.
e. Insert a thin-bladed screwdriver into the hollow valve stem
and engage the slotted screw inside (Shoto B)
Flame size can be increased or decreased with the turn of the screw.
Turn counterclockwise to increase flame size. Turn clockwise to
decrease flame size. It may be necessary to hold the shaft securely ZLWK
pliers or adjustable wrench to turn the adjustment screw.
Photo B
2:18