I have a OS-46 that runs great. The problem is: when I pull the throttle back to idle-the motor slows down, then then after about 5 sec. It slows down more. If I set the idle where I want it when it slows down then it quits. Any suggestions. Like I say the motor runs great, good transition, WOT is good

That is usually a sign of being too rich on the low end.

At WOT the mixture is good but the needle valve is set slightly lean to compensate for the extra amount of fuel coming in from the low end adjustment, so when you throttle up, the transition is good.

Now you go back to idle, and the mixture slowly richens.

Try adjusting the low end by 1/8-turn increments. You'll have to richen the high end slightly each time too

I will do that Sir. Thanks for the information. So I am going to lean the lsn and richen the hsn is that correct?

Correct

Once you get the low speed set like Minnflyer pointed out, that .46-AX will idle long, long periods of time with no sign of quitting.