Rebuild your carb again.
OEM Kits are cheap.
For a 1994 15hp :
First link and sync back to factory settings (very important) . Drop your idle RPM.
Lightly seat the lean rich screw then turn counter clockwise 4 full turns.
Turn clockwise in 1/4 turn increments waiting 15 seconds each time for the engine to respond.
You are looking for the highest RPM.
When it sputters or coughs, immediately turn the needle counter clockwise.
Look again for the highest RPM.
Once you've found the highest RPM add a 1/4 turn counter clockwise ( factory specs calls for an additional 1/8th turn) to prevent a lean condition.
You're done.
Don't ever touch the screw again.
Factory service manual recommends 3 full turns.
Leroy recommends 4.5 turns.
I use anywhere from 3 to 4 turns more or less depending on the condition of your needle.
Pre-92 uses 1.5 turns.
