You don't really need a tach to set the motor for a rich
enough setting....you can tell by the sound. Start the
motor at about 1/3 throttle, and let it warm up for
about 20 seconds. Open the throttle all the way, and turn
the needle in....till the motor starts to slow down. Quickly
open the needle a few clicks, and it will be running full
speed again....now open the nedle till the motor "audibly"
slows down a bit....you can hear it. Now you are running a
bit rich....right where you want to be. The amount of
richness you need depends on varying factors....but the
bottom line is....you always want it running a bit rich to
avoid over heating the motor.

Ask one of the fellas at the field how to set your motor
on the rich side....if it is too rich, it will be low on power,
and will waste fuel....but generally it will not hurt the motor.

Your motor is an ABN type....(nickel plated bore)....not a
ABC....(chrome plated bore)....which is more durable,
But it is a good motor.

Dave.