OS 120 and 160
 

I have an OS 120 AX and 160 FX both engines exhibit a rich midrange (idle an top end are good), have tried to lean down idle and top end as far as possible and still have engine run ok but can't eleminate rich half throttle condition. Using standare OS mufflers for the engines and 15% fuel with recommended glow plugs.

These engines are in 3D planes and at hover power they both run rich and the engines burble, this makes throttle response slow when pulling out of hover when going to full throttle.

Can the mid-range be cleaned up for better throttle response?

WRK

RE: OS 120 and 160
 

You can try a few things....

Try a smaller prop to get the max RPM somewhat higher. You'll then have to re-do the needles, and this may cure the difficulty.

Get more pressure to the tank, and you'll have to re-do the needles, too. This may work out because you'll have to lean the idle mixture to get a good idle with higher fuel tank pressure.