My 148 will appear to be very rich on the ground especially before it has run at full throttle for several seconds. I set mine to hold full rpm then richen it about 1/4 turn. It then winds up in the air.

I use 5% nitro 2% castor 15% synthetic 18x6W APC. I have had two 148s the early one with the mark 1 carb had a flat spot mid range, the second one with the MDS mk2 carb is great. I set the needle at the beginning of the summer and it runs all year. It is in a 70in span 3 D fun fly and you need a reliable throttle in the hover.

Check your fuel lines esp the clunk line.