Originally Posted by
Hobbsy
This is the carb I use on the ST .90 conversion. It is a .61 size carb with the thin spray bar. Maybe someone can enlighten me because it may be the stock carb. Thanks, Dave
It likely is the stock carb. It appears your carb is a later model carb as it has the idle needle recessed into the barrel and has a plastic throttle arm. The old ones have the idle needle external to the barrel that you can turn with your fingers or a screwdriver and has a metal throttle arm.
My G51 has the same carb your .90 has except the spraybar was round originally. The choke diameter should be about 8.9mm.