I have a 91 surpass rann great last year,
this put it into new plane and starts ok but as i throttle up it backfires and spits the prop.

new OS F plug
new 15% fuel
fed it from clean hopper tank
backflushed carb with fuel
still back fires

oK took carb apart for cleaning

assembled with low end 3 turns out & high 3 turns out

and then opend them up some to get it to fire

still backfired & lost prop nuts

Correct starting needle settings needed or is it time to buy a Saito?

SO FRA THIS ENGINE HAS CONSUMED:
1 SPINNER
2 PROPS
2 PROPNUT SETS
TOO MUCH OF MY TIME

First off, get the carburetor set according to the instructions. These are the rough, "ballpark" starting positions. You then adjust from there as needed. If you don't have the instructions, then please send an email to the address below, and we can send you a set. We can't describe the setting because you need a diagram. It's in the instruction sheet.