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- Apr 17, 2012
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Most of the engine discussions here focus on higher powered engines, but I know some of you have wide experience.
The Jodel has a C-85. After tweaking the ground-adjustable prop a bit, it turns pretty close to red line in level flight, and the prop is set to what seems like a reasonable pitch. Climb seems a little anemic, but I don't have any basis for comparison to know how it should climb. Overall, I think the engine is running pretty good. Seems like it is burning about 5 - 6 gallons per hour - haven't checked it really closely.
The odd thing is the throttle response. The first half of the throttle travel gets a linear response, but there is essentially no change in RPM for the last half of travel. I have verified that the carb butterfly is closed at min throttle, and wide open at max throttle, and there isn't any slop in the linkage - just enough overtravel in the throttle lever that the carb lever is sure to hit its stop. But when I level off and throttle back, RPM doesn't drop till the throttle is half-way back.
It has a Stromberg NA-S3 carb. I've read what I can find on that, and the only thing that I've found that seems like a possible cause is that on some of them, the float needle doesn't open as far as it should. But it seems like if the fuel flow was restricted, the thing would lean out and run rough - at least it seems like the difference in air flow between the butterfly being half open and wide open would be enough to cause a serious lean condition.
Any ideas as to what could cause this?
Thanks!
Warren
The Jodel has a C-85. After tweaking the ground-adjustable prop a bit, it turns pretty close to red line in level flight, and the prop is set to what seems like a reasonable pitch. Climb seems a little anemic, but I don't have any basis for comparison to know how it should climb. Overall, I think the engine is running pretty good. Seems like it is burning about 5 - 6 gallons per hour - haven't checked it really closely.
The odd thing is the throttle response. The first half of the throttle travel gets a linear response, but there is essentially no change in RPM for the last half of travel. I have verified that the carb butterfly is closed at min throttle, and wide open at max throttle, and there isn't any slop in the linkage - just enough overtravel in the throttle lever that the carb lever is sure to hit its stop. But when I level off and throttle back, RPM doesn't drop till the throttle is half-way back.
It has a Stromberg NA-S3 carb. I've read what I can find on that, and the only thing that I've found that seems like a possible cause is that on some of them, the float needle doesn't open as far as it should. But it seems like if the fuel flow was restricted, the thing would lean out and run rough - at least it seems like the difference in air flow between the butterfly being half open and wide open would be enough to cause a serious lean condition.
Any ideas as to what could cause this?
Thanks!
Warren
