Try the idle mixture control screw at 1 1/4 turn on a fresh engine. Once you get 500 or so miles on the engine, should be able to get it down to 1 turn.

Hand throttle cable brackets are tough to find; since this is a non-stock application - make one, not that difficult.

Jon.

Good carburetion is fuelish hot air
The most expensive carburetor is the wrong one you attempt to modify.
If you truly believe "one size fits all," try walking a mile in your spouse's shoes!
The Carburetor Shop