Debra
11-29-2007, 03:40 PM
I would appreciate your opinion. I purchased a used airplane with
a 3 year Magnum 120 4-stroke (RFS). It runs well with well
adjusted low and high end settings. I ran a tank of fuel through
it to determine the run time and the engine stalled after 8
minutes (at full throttle). There was still a small amount of
fuel in it that should have burned. I noticed that the prop
spinner (aluminum back plate with a plastic cone) was so hot that
I could not touch it for about 30 minutes. I restarted the plane
a few hours later and it burned off the remaining fuel.
I am concerned that it stalled because of overheating. I can
certainly richen the high end setting. I was using the maximum
prop size (16x8). Why would this engine be over heating and
stalling after just 8 minutes? Is it a problem with this type of
Magnum motor or is there something wrong with the engine itself or
will the conditions change when flying with forward airspeed and
throttle variation? All of my other motors are OS and YS and they
never flame out.
Thank you for your response.
John in Phoenix
Dear John,
If it takes 30 minutes for your engine to cool down, this a definite indication that you are running it far too lean or your fuel, which you did not mention, does not contain sufficient lubrication. Also, a 16 x 8 is also a pretty good load for a three year old engine that has probably seen a lot of wear.Try a 15 x 8.
The 4-strokes are not particularly noted for their fuel draw ability and, as such, fuel tank position is more critical. You may have your fuel tank positioned too low. Ee sure that the center line is even with the carburetor needle valve. Muffler pressure is also necessary, so be sure this is connected and not being pinched off by a hatch cover, etc. If the tank isn't venting, the engine is going to lean out. If the tank position is okay and the pressure line not shut off, then try another brand of fuel or add two or three ounces of castor oil to your fuel and run the engine richer. Be sure the fuel you are using contains no less than 18% lubrication, Many 4-stroke fuels do not. Let us know if this solves the problem.
Yours,
Clarence Lee
a 3 year Magnum 120 4-stroke (RFS). It runs well with well
adjusted low and high end settings. I ran a tank of fuel through
it to determine the run time and the engine stalled after 8
minutes (at full throttle). There was still a small amount of
fuel in it that should have burned. I noticed that the prop
spinner (aluminum back plate with a plastic cone) was so hot that
I could not touch it for about 30 minutes. I restarted the plane
a few hours later and it burned off the remaining fuel.
I am concerned that it stalled because of overheating. I can
certainly richen the high end setting. I was using the maximum
prop size (16x8). Why would this engine be over heating and
stalling after just 8 minutes? Is it a problem with this type of
Magnum motor or is there something wrong with the engine itself or
will the conditions change when flying with forward airspeed and
throttle variation? All of my other motors are OS and YS and they
never flame out.
Thank you for your response.
John in Phoenix
Dear John,
If it takes 30 minutes for your engine to cool down, this a definite indication that you are running it far too lean or your fuel, which you did not mention, does not contain sufficient lubrication. Also, a 16 x 8 is also a pretty good load for a three year old engine that has probably seen a lot of wear.Try a 15 x 8.
The 4-strokes are not particularly noted for their fuel draw ability and, as such, fuel tank position is more critical. You may have your fuel tank positioned too low. Ee sure that the center line is even with the carburetor needle valve. Muffler pressure is also necessary, so be sure this is connected and not being pinched off by a hatch cover, etc. If the tank isn't venting, the engine is going to lean out. If the tank position is okay and the pressure line not shut off, then try another brand of fuel or add two or three ounces of castor oil to your fuel and run the engine richer. Be sure the fuel you are using contains no less than 18% lubrication, Many 4-stroke fuels do not. Let us know if this solves the problem.
Yours,
Clarence Lee