So my new plane i just built the only way i can install the engine is inverted what kind of problems will i have? Cant wait to see pics of this thing.
There are a few things to know about the nature of setting up and running any engine inverted. RC engines are small, lightweight and fairly simplistic engines. They do not have all the complex equipment available to competition aerobatic full size aircraft engines or similar machines; therefore, when asked to run in inverted mounting, sometimes they can be a bit more challenging to set up than an upright installation.
First, realize that your engine may be full of fuel PRIOR to starting, risking hydrolock which can do severe damage to your engine, especially if the aircraft has been stood on its nose or even just nose low during transportation. Always flip the prop over to check the compression prior to using a starter. If it seems harder than normal, remove the glowplug and flip through several times or spin the engine with an electric starter to clear it and avoid the possibility of hydrolock.
Next, ALWAYS follow your manufacturer's instructions on engine break-in. In almost every case, the engine should be broken in on a test stand where it can be properly watched, cared for, fueled, drained, and adjusted easily and safely. If your manufacturer recommends in flight break-in, just be aware that it will be soft on power until the break-in period is completed and always be prepared for a dead stick landing during those break-in flights.
Then, once it is broken in, it can be installed. Please note that it is best to try to locate your engine so that the needle valve is in line with the centerline of the fuel tank if possible.
In some cases tuning in the inverted installation is a little more challenging due to the tank/carb relationship combined with the inverted mounting. If this is the case, tuning with the aircraft inverted/engine upright will help get the engine running flawlessly, then it can be run inverted.
Finally, some engines, especially inexpensive bushinged budget engines, will not like to start in an inverted position, again due to carb/tank positioning and fuel flow. In those case, you may need to start the aircraft inverted and turn upright to fly when running.