OS FS Surpass II 91 Pump engine

[ahdofu]

I am not into racing but I have noticed a drop in the performance of the airplane. It is not as agile as it used to be in full throttle.
Once new fuel comes in I'll buy some. In the meantime I'll use whatever I have.

 

[ahdofu]

I think I have finally solved my issue. I systematically replaced the O-rings on the needle, mixture control valve and the carb/intake manifold and the last one did it! Peak RPM is now 9600 and the motor seems to be fully functional. I'll call it good once I've had a few flight cycles with good motor behavior.

 

[Konrad]

The carb to manifold O-ring?

 

[ahdofu]

Where I have circled there is an O-ring in between the mating surfaces of the carb and the intake pipe. (Bad choice of words as I called this manifold). The old one had gotten stiff and I guess allowed some leakage to occur.

 

[Konrad]

We, well I'm not a word smith. I know manifold means "one into many" but to us gear heads we know what you mean.

Now a leak where shown should not effect power as you should be able to adjust the fuel mixture by hand for the air that is bypassing the carb (spray bar). A leak there will wreck havoc with tractability.

 

[ahdofu]

Correct. That is why sometimes peak RPM occurred at 2-3 turns and sometimes at 1+ turns. Of course other factors like engine vibration and/or having fuel/oil at the mating surface may have affected how well the old seal functioned. When I was replacing the O-ring the intake pipe slid out with ease. With the new O-ring, it is now held tightly in place. As I said once I've had a few flights I'll know whether this was it or not.

 

[ahdofu]

Had a great experience at the field today. No issues whatsoever with the engine. Another thing that I noticed was that previously the motoring took a while before the engine started. Now the engine starts quickly. Thanks for all of your comments & feedback Konrad.