OS 61 FX carb
05-19-2010, 01:23 AM
#1
OS 61 FX carb
Bill,, 2 things about my OS 61 FX here,,
A) is there a Larger Carb that is a pop-in fit for the 61FX ?? even a different brand Carb would be OK with me,, keep in mind I'm a Heli guy too so I'm not afraid of modifying an Engine with a larger Carb,,
I am looking to get a few 100 RPMs more without changing the Muffler, this Engine is in a GP 60 size Shoe String, and it has a rather small Tubular type Pitts Muffler,,
to add it only has 5 Gallons run threw it and it has very good Compression..
I have an APC 12x6 on it, an APC 12x8 is to much Prop, it will only turn the 12x8 to 8800 (tuned for flight), and the Plane comes in Super Hot on the Landings with the 12x8 so I want to use the 12x6..
B) (till I get a larger Carb) I'm having a problem with the stock Carb, the Engine keeps stalling right after landing, 10 flights 10 stalls right after Landing,,
I thought the Idle was lean a little bit cause after it Warmed-up on the Ground the Idle would Hang High a bit, so I richened the Idle Screw 1/8th then later 1/8th more, I changed the OS 8 to a K&B Medium and it seams to Idle better and accelerate better, even sound smoother/more constant at Idle, I even feel I got a bit more power with the K&B Plug, but on the next flight it Stalled/Flamed-out in the Air on the Landing,, I plain to remove the Cowl this Weekend and do the Pinch Test,, Fuel is Magnum 15%..
can I get some comments please ??
thanks !!!
Jim
A) is there a Larger Carb that is a pop-in fit for the 61FX ?? even a different brand Carb would be OK with me,, keep in mind I'm a Heli guy too so I'm not afraid of modifying an Engine with a larger Carb,,
I am looking to get a few 100 RPMs more without changing the Muffler, this Engine is in a GP 60 size Shoe String, and it has a rather small Tubular type Pitts Muffler,,
to add it only has 5 Gallons run threw it and it has very good Compression..
I have an APC 12x6 on it, an APC 12x8 is to much Prop, it will only turn the 12x8 to 8800 (tuned for flight), and the Plane comes in Super Hot on the Landings with the 12x8 so I want to use the 12x6..
B) (till I get a larger Carb) I'm having a problem with the stock Carb, the Engine keeps stalling right after landing, 10 flights 10 stalls right after Landing,,
I thought the Idle was lean a little bit cause after it Warmed-up on the Ground the Idle would Hang High a bit, so I richened the Idle Screw 1/8th then later 1/8th more, I changed the OS 8 to a K&B Medium and it seams to Idle better and accelerate better, even sound smoother/more constant at Idle, I even feel I got a bit more power with the K&B Plug, but on the next flight it Stalled/Flamed-out in the Air on the Landing,, I plain to remove the Cowl this Weekend and do the Pinch Test,, Fuel is Magnum 15%..
can I get some comments please ??
thanks !!!
Jim
05-19-2010, 08:53 AM
#2
My Feedback: (11)
RE: OS 61 FX carb
First off, you didn't say what RPM you're currently running. If you want more in-flight speed, a larger carb won't help. You'd also need to add a pump because the larger carburetor would have a much lower fuel draw. What you really want to do is go to something like an 11 x 7 or 11 x 8 propeller. Turn the engine up! What makes for speed is RPM. The smaller props will also allow for better landing because they'll have less "pull" at low speeds. You should have no trouble getting the engine to turn over 12,000 RPM with the right prop.
As far as the quitting upon landing, it could be anything from a cracked line that's exposed when the fuel level goes down to a badly-positioned fuel tank.
For carb adjusting, you want to start out with the idle mixture at a "stupid rich" setting. Open the high-speed needle to a very rich setting and start the engine at part throttle. Open it to full throttle and get the high-speed needle set to just rich of peak RPM. Then, retard the throttle and work with the idle mixture.
If all else fails, remove the engine from the airplane and put it on a test stand. Run it there with the fuel system all set up correctly with good components. If the engine runs well on the bench, but not in the plane, it's not the engine that has a problem, but the fuel system/airframe/engine combination.
You may also find that your exhaust system is too restrictive and not allowing the engine to reach its full potential.
As far as the quitting upon landing, it could be anything from a cracked line that's exposed when the fuel level goes down to a badly-positioned fuel tank.
For carb adjusting, you want to start out with the idle mixture at a "stupid rich" setting. Open the high-speed needle to a very rich setting and start the engine at part throttle. Open it to full throttle and get the high-speed needle set to just rich of peak RPM. Then, retard the throttle and work with the idle mixture.
If all else fails, remove the engine from the airplane and put it on a test stand. Run it there with the fuel system all set up correctly with good components. If the engine runs well on the bench, but not in the plane, it's not the engine that has a problem, but the fuel system/airframe/engine combination.
You may also find that your exhaust system is too restrictive and not allowing the engine to reach its full potential.
05-19-2010, 02:12 PM
#3
RE: OS 61 FX carb
OK thanks !!
just a fallowup,,
""you didn't say what RPM you're currently running""
LOL didn't think to,, well I did tack it with the 12x6 and it was right around 12,000, not sure just what tho,,
yeeaa I ran Glow and Gasser RC Boats so I understand small Diameter more Pitch more RPM more Speed (within reason), just didn't think about how a smaller 11x8 wouldn't pull as much on landings, but understand,, as I said I will pull the Cowl off this weekend and and work on it..
thanks again !!
Jim
just a fallowup,,
""you didn't say what RPM you're currently running""
LOL didn't think to,, well I did tack it with the 12x6 and it was right around 12,000, not sure just what tho,,
yeeaa I ran Glow and Gasser RC Boats so I understand small Diameter more Pitch more RPM more Speed (within reason), just didn't think about how a smaller 11x8 wouldn't pull as much on landings, but understand,, as I said I will pull the Cowl off this weekend and and work on it..
thanks again !!
Jim
05-24-2010, 07:27 PM
#4
RE: OS 61 FX carb
a fallow up here,,
well to make a 4 hour story short, "my OS 61 FX was to Rich",,
the Pinch Test did not help, while doing the Test the Idle did not change until a count of 6, so because the RPMs would not come up we assumed it was Lean a bit, so after Pinch Testing and Richening it many times I put the Idle Screw back to where it was originally and then leaned it even more and the Transaction to Full Throttle became smooth, happy happy joy joy,,
Prop,, so hoping for more Top Speed (as suggested) I went down from the APC 12x6 to an APC 11x8, sorry I did not Tach the RPMs but it was very noticeable the RPMs did come up with the 11x8, BUT I did not get an increase in Top Speed, in-fact I feel I lost a bit of Top Speed..
Jim
well to make a 4 hour story short, "my OS 61 FX was to Rich",,
the Pinch Test did not help, while doing the Test the Idle did not change until a count of 6, so because the RPMs would not come up we assumed it was Lean a bit, so after Pinch Testing and Richening it many times I put the Idle Screw back to where it was originally and then leaned it even more and the Transaction to Full Throttle became smooth, happy happy joy joy,,
Prop,, so hoping for more Top Speed (as suggested) I went down from the APC 12x6 to an APC 11x8, sorry I did not Tach the RPMs but it was very noticeable the RPMs did come up with the 11x8, BUT I did not get an increase in Top Speed, in-fact I feel I lost a bit of Top Speed..
Jim
