O.S. 55AX Inverted Mount Problems
 

I recently added a new O.S. 55AX to my Ultrasport Plus, I mounted it inverted and added an onboard ignition system. I am using 15% nitro fuel with 18% oil and a O.S. 8 glow plug. I am trying to get the engine running properly but I'm running into many issues. First of all, the carburetor seems to flood often, when I do get the engine running, I advance the throttle and it quits once the ignition system turns off. I've adjusted the high-end needle valve to the lean side but it's still giving me a lot of issues, spitting out a lot of unburned fuel, etc. I was told to run a 3-line fuel tank, use 30% nitro, use an O.S. F plug and lean out the idle screw. I don't fully understand the 3 line fuel tank, running two clunks, one to the muffler, one to the carburetor and plug the vent line.

Any helpful suggestions would be greatly appreciated.

Bill

RE: O.S. 55AX Inverted Mount Problems
 

Get the engine set up properly upright, first. You need the high-speed and low-speed settings for upright operation...that's because they're easy to get set in that configuration. Then mount the engine inverted. Flooding is normal with inverted installations. You'll need to clamp-off the fuel line when you're not running, or make sure the fuel level's lower than the carb. Even so, at low throttle operation, the engine can be problematic. With a #8 plug and an onboard system, you should be OK. Idle and acceleration are what become problematic with inverted running.

If the engine's not well-broken-in before it's mounted inverted, you'll likely have problems. It should be well-broken-in before you use it in anything but upright or side-mounted.