Ratio Tool is pre calibrated. Do
not attempt to move
dial indicator face.*
Remove three screws from top of carburetor, and remove slide.
Remove slide from cable. (Please do one carburetor at a time
so you do not mix up which slide goes into which carburetor.)
Lift up on dial indicator probe and insert slide assembly.
(Make sure slide and metering rod is fully in and seated; you may
want to tug on rod to be sure it is all the way in.) See figure
Turn rod to the left & right to find lowest point on
indicator. Read indicator as you are doing this. If it does not read
“0” at the lowest point, an adjustment is required. See
slide in one hand and with other hand simply screw rod ¼ of a turn
(turn rod in it richens carburetor and turn rod out it leans
carburetor) you might need the # RT-1 or a pair of needle nose
pliers to turn the rod. Now that you made your adjustment, you must
return the flat part of the rod to proper position. The rod will not
work unless the flat side of the rod faces the intake side of the
engine. You will not
need the RT-1 or pliers for this job.
the slide in your left hand, grab the rod with your other hand and
push up on the rod, return it so the flat side is facing the intake
are done with your adjustment!
carburetor and repeat idle tuning steps.
Adjust metering rod until dial indicator reads “0”.
Adjust idle slide height as necessary for proper idle speed.
Note: if dial indicator face gets moved by accident, you may
recalibrate tool by inserting rod in backside of tool with round
side up. Indicator should read +.006” for 44mm or smaller
and +.0065” for 46mm and bigger. See
In some cases because of improper spark or low compression, it is
possible that you may have to adjust the metering rod ¼ of a turn
leaner or richer (but no more), to obtain proper plug color.