adjusting sj413 carb

[luke25]

My choke on my carb wasn't having any effect which was ok till it got a bit colder recently. Rather than try to fix the problem I just replaced the carb with a spare one I had with a working choke. As soon as I started up I found that the engine idles at about 2500rpm even with the throttle linkage adjusted to fully closed and slack in the cable. I'm guessing this means the mixture is really rich at idle? Does anyone know how to adjust these carbs?