I have two(2) motors (Fox Part # 35015) that I purchase new a couple of years ago along with two (2) Hemi head and backplte conversion kits.
The Hemi KOP's were installed and the motors broke in on a bench and then put on the shelf for future use.
Bench running time on each was 90 min. using 16 ozs. of fuel.

Recently I installed the motors on a RSM Ring Master and a Brodak Magician. Each plane utilizes a Brodak 3.5 oz uniflow fuel tank setup and 2 degree engine offset. Each motor incorporates a single port Fox spray bar and needle valve. The spray bar port faces down in the venturi toward the crankshaft I have the needle valve opened 4.5 turns. There is no pressure setup on either aircraft.

Both motors start easy with a 4-cycle idle. Each motor goes to a 2-cycle with nose up and back to a 4-cycle nose down when held on the ground.
The motor continues to run when the aircraft is held inverted.

PROBLEM: Each motor runs correctly in level flight and performing a standard wingover flying counter clockwise.
              Both motors shut off when the aircraft goes inverted and begins its CLOCKWISE flight. It does not matter if you
              enter inverted flight from an inside loop or outside loop. The result is the same, motor shutdown.
              I changed to a Sullivan Plastic tank setup with fill, overflow and pickup tube configuration and experienced the same result.

All input and ideas is appreciated.

I have two(2) motors (Fox Part # 35015) that I purchase new a couple of years ago along with two (2) Hemi head and backplte conversion kits.
The Hemi KOP's were installed and the motors broke in on a bench and then put on the shelf for future use.
Bench running time on each was 90 min. using 16 ozs. of fuel.

Recently I installed the motors on a RSM Ring Master and a Brodak Magician. Each plane utilizes a Brodak 3.5 oz uniflow fuel tank setup and 2 degree engine offset. Each motor incorporates a single port Fox spray bar and needle valve. The spray bar port faces down in the venturi toward the crankshaft I have the needle valve opened 4.5 turns. There is no pressure setup on either aircraft.

Both motors start easy with a 4-cycle idle. Each motor goes to a 2-cycle with nose up and back to a 4-cycle nose down when held on the ground.
The motor continues to run when the aircraft is held inverted.

PROBLEM: Each motor runs correctly in level flight and performing a standard wingover flying counter clockwise.
              Both motors shut off when the aircraft goes inverted and begins its CLOCKWISE flight. It does not matter if you
              enter inverted flight from an inside loop or outside loop. The result is the same, motor shutdown.
              I changed to a Sullivan Plastic tank setup with fill, overflow and pickup tube configuration and experienced the same result.

All input and ideas is appreciated.

David

Does it go lean and shut off, go rich and die or burp and shut off?
It is typical that you need to raise the fuel tank about 3\16 inch above centerline when using a FOX 35 on a profile. is you tank level with the spraybar or above it?

Randy

If you are using the Fox standard plug that came with the engine, that will cause it to do that even with the bypass mod on some engines. I would recommend a Thunderbolt long R/C, Glo-Devil 300, K&B long R/C, or even a Fox long R/C plug. It may still burp, but hopefully will not quit. I assume you are using fuel with at least 25% castor.

Jim,

FUEL - Fox Fuel, Nitro=10%; Castor=20%; Synthetic=0%;Methanol=70%
Plug - Standard Fox Long that shipped with the Motor.

As I stated in my Email, I will bump up the castor to 25% and change to the plug I
use in my other motors, the SIG RC long, Part number SIGGP003.

In addition, I Emailed Fox Mfg. just to see what their input to the problem will be.

David

Hi David

You really need at least 25% oil in the FOX, and a HOT plug, the ones mentioned SIG RC long, T Bolt RC Long, T BOlt Big Borem Enya #3 are just a few that work well. Try these and let us know how things are going
One other thing you can do ,If you have a tach, hold the plane rightside up, tach the motor then do the same inverted and back to rightside up, do this a few times and record what RPM differance you see
Randy