my 40la engine that i put on my 25 size me-109 inverted seemed to be having less rpm's and that it has reduced horsepower...i suspect that it's because that the engine is inverted and because of how the fuel leaks out of the carburetor when it is inverted....is it just me or is this common to some of you guys too?...Can anything be done to correct this or are two strokes really weaker when it comes to being inverted?

Hi,

It is more likely that the motor is loosing power through overheating in a fully cowled location, reather than from being inverted. Try to ensure there is adequate airflow through the cowling and run the motor a little richer than in an "open" situation.

Cheers,

Colin

Ditto, inverted shouldn't rob power. About the only issue with inverted engines is they sometimes are hard to start if the plug is soaked with oil. Some fuel may dribble or spray out of the carb when running, this is fairly normal as long as it is not excessive. Likewise, if the carb is below the tank line, you may have some fuel siphon out when the engine is off, also normal. Like mentioned above, I'd look into cooling issues.

General rule is that 4 strokes don't seem to mind running inverted. 2 strokes don't like it and it creates more problems than you need! []

For what it's worth, the "general rule" with 2-cycle engines in control line stunt competition is that the engine is almost always inverted. There is no loss of power. Starting is not a problem. A 2-cycle engine doesn't "know" if it is upright, inverted, profile-mounted, or at an angle. They are mounted in all these configurations on RC and C/L planes. Look elsewhere for any loss of power. (Old fuel, old plug, tank location, cooling provisions.) Good luck, Dzl

The oil that is in the fuel for lub and cooling due to gravity tends to start to collect in cyclinder at lower rpms. At full throttle there is enough exhaust to blow it out the muffler which is why CL engines whcih run at full throttle for the full flight don't seem to have a problem. When the oil collects at lower rpms, it will start to douse out the glow plug and you will lose power and eventually the engine will quit unless you throttle up again. The 4 strokes operate differently and once started are pretty trouble free even when inverted.

Oh ok thanks alot...its just my engine seems so much more quiet in the air than when it was before in my trainer....

My engine definitely has no trouble with cooling...i mean the whole front of the cylinder is out there and so it sticks out of the cowling...it never quit on me due to any overheating...and the tank is perfectly centered with the needle valve....and starting is easier after having run 3 tanks on it.

Good to hear there's no problem in the inverted position then...

The "quietness" MAY be due to the fact you are running a different prop. APC props are quieter than MAS props (also more efficient ).

Again, the lower rpms may be due to the prop AND/OR the fact that you are actually using less rpms. You have a 40 size engine (granted it only has the power of a 30 - 35 ) in a 25 size plane. Due to its size, the plane may APPEAR to be going faster than it really is so you are using less throttle to achieve what you perceive as the proper flying speed (a speed you are comfortable with ).