OS 61 FX needle valve/fuel inlet positioning
01-22-2003, 04:39 PM
#1
OS 61 FX needle valve/fuel inlet positioning
Let me begin by saying what an excellent job of providing support you are providing through the use of this medium. Thank you for all of the time and effort it must take to stay on top this.
I own a 61FX that I just installed in a new airplane. The engine is brand new and was broken in exactly as indicated in the owners manual using the ten second intervals. I am experiencing some problems with the engine going lean at mid range and top end when in the air. I resolved the top end issue by adjusting the mixture setting much more to the rich side but, once in the air the top end settles down and runs at expectation while the midrange still remains lean -- I get sort of a frying egg kind of crackle when I pull the engine back to midrange.
I believe the problem may be air intrusion somewhere at the fuel inlet or needle valve. The fuel tank is completely surrounded by foam and upstream of the fuel tank I don't see any evidence of bubbles. Downstream of the needle valve I do see bubbles. I pulled everything apart, cleaned and reassembled but still have the problem.
My next solution attempt is to rotate the needle valve from the vertical position to the horizontal - it came in the vertical position. Your online manual and the manual that came with my engine as well as the way my engine was configured when it arrived are different in that the online manual (page9) shows the fuel inlet to always be installed not in line with the needle valve but rather installed in the hole not being used by the needle valve. Whereas, the fuel inlet for the 50SX/91FX (same page) have the fuel inlet installed in line with the needle valve when the needle valve is in the vertical position. My original owners manual shows the fuel inlet to always be installed on the vertical inlet regardless of the location of the needle valve.
I am trying to sort out what is the correct assembly postion(s) of the fuel inlet when the needle valve is horizontal and when vertical for the 61 FX.
Once I try the flying with the needle valve in the horizontal position to resolve the in flight leaning problem I will let you know the results.
[email protected]
Thank you.
Howard
I own a 61FX that I just installed in a new airplane. The engine is brand new and was broken in exactly as indicated in the owners manual using the ten second intervals. I am experiencing some problems with the engine going lean at mid range and top end when in the air. I resolved the top end issue by adjusting the mixture setting much more to the rich side but, once in the air the top end settles down and runs at expectation while the midrange still remains lean -- I get sort of a frying egg kind of crackle when I pull the engine back to midrange.
I believe the problem may be air intrusion somewhere at the fuel inlet or needle valve. The fuel tank is completely surrounded by foam and upstream of the fuel tank I don't see any evidence of bubbles. Downstream of the needle valve I do see bubbles. I pulled everything apart, cleaned and reassembled but still have the problem.
My next solution attempt is to rotate the needle valve from the vertical position to the horizontal - it came in the vertical position. Your online manual and the manual that came with my engine as well as the way my engine was configured when it arrived are different in that the online manual (page9) shows the fuel inlet to always be installed not in line with the needle valve but rather installed in the hole not being used by the needle valve. Whereas, the fuel inlet for the 50SX/91FX (same page) have the fuel inlet installed in line with the needle valve when the needle valve is in the vertical position. My original owners manual shows the fuel inlet to always be installed on the vertical inlet regardless of the location of the needle valve.
I am trying to sort out what is the correct assembly postion(s) of the fuel inlet when the needle valve is horizontal and when vertical for the 61 FX.
Once I try the flying with the needle valve in the horizontal position to resolve the in flight leaning problem I will let you know the results.
[email protected]
Thank you.
Howard
01-22-2003, 05:26 PM
#2
My Feedback: (11)
OS 61 FX needle valve/fuel inlet positioning
Howard,
Regardless of whether you put the needle valve in the horizontal or vertical position, the tank position remains the same. It should be positioned in relation to the center of the carburetor, where the fuel enters the venturi. The needle is often reffered to because it's big and easy to use, and was positioned on the carb on most engines for so long.
If the engine's trending lean in the air, the fuel system is usually the culprit. With most engines, throttling down will richen the mixture, and not lean it. If the engine's going lean, you'll have to search for the problem.
Fuel foaming is most common, and shouldn't be discounted, even if you've foamed the tank and see no bubbles. You may not see the bubbles, since they are many times micro-sized. Foam can be too much or too little. Tubing can be cracked or have a pinhole.
You may need to check your muffler tap and tubing. We've seen the muffler tap blocked by trash or congealed fuel residue. That would also make the engine go lean. If it's blocked too much, the engine will quit from being too lean.
An air leak would make itself known more at higher throttle settings when the engine is drawing harder on the fuel. If you see no air bubbles between the needle and the carb, then the needle's not leaking.
Finally, is the engine sounding lean because it's overheating? Is your fuel fresh and moisture-free? Is enough cooling air getting around the engine?
A lot of these things may be obvious, and you might already have checked them all, but I've listed these things for everyone else who's having some leaning problems.
Finally, remember that if the engine will run nicely on the ground at all throttle settings, and doesn't show problems there, then it's not the engine, itself. The problem is in the engine/mount/fuel system/airframe combination.
Regardless of whether you put the needle valve in the horizontal or vertical position, the tank position remains the same. It should be positioned in relation to the center of the carburetor, where the fuel enters the venturi. The needle is often reffered to because it's big and easy to use, and was positioned on the carb on most engines for so long.
If the engine's trending lean in the air, the fuel system is usually the culprit. With most engines, throttling down will richen the mixture, and not lean it. If the engine's going lean, you'll have to search for the problem.
Fuel foaming is most common, and shouldn't be discounted, even if you've foamed the tank and see no bubbles. You may not see the bubbles, since they are many times micro-sized. Foam can be too much or too little. Tubing can be cracked or have a pinhole.
You may need to check your muffler tap and tubing. We've seen the muffler tap blocked by trash or congealed fuel residue. That would also make the engine go lean. If it's blocked too much, the engine will quit from being too lean.
An air leak would make itself known more at higher throttle settings when the engine is drawing harder on the fuel. If you see no air bubbles between the needle and the carb, then the needle's not leaking.
Finally, is the engine sounding lean because it's overheating? Is your fuel fresh and moisture-free? Is enough cooling air getting around the engine?
A lot of these things may be obvious, and you might already have checked them all, but I've listed these things for everyone else who's having some leaning problems.
Finally, remember that if the engine will run nicely on the ground at all throttle settings, and doesn't show problems there, then it's not the engine, itself. The problem is in the engine/mount/fuel system/airframe combination.
