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OS 91FS needle settings
I have an OS FS-91SII-P that I am having problems setting the high speed needle valve. It seems to run and fly well at 1 1/4 turns out and has a good smoke trail, but if I do a pinch test, seems lean. And according to the original setting of the needle valve and advice from product support seems to be on the lean side. Any advice? Also, there seems to be a lot of raw fuel on the engine and under the cowl. I have tried richening the engine and it gets extremely sluggish and wants to pull down in RPM's and eventually backfires, spinning the prop loose. The engine has around a gallon of fuel through it, and at the leaner settings, idle's fine and seems to fly well, I just don't want to run it too lean. Thanks for any advice!
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RE: OS 91FS needle settings
ORIGINAL: zoner I have an OS FS-91SII-P that I am having problems setting the high speed needle valve. It seems to run and fly well at 1 1/4 turns out and has a good smoke trail, but if I do a pinch test, seems lean. And according to the original setting of the needle valve and advice from product support seems to be on the lean side. Any advice? Also, there seems to be a lot of raw fuel on the engine and under the cowl. I have tried richening the engine and it gets extremely sluggish and wants to pull down in RPM's and eventually backfires, spinning the prop loose. The engine has around a gallon of fuel through it, and at the leaner settings, idle's fine and seems to fly well, I just don't want to run it too lean. Thanks for any advice! The pinch test does not work so well on pumped engines Backfiring is a sign of being too lean Lean is running less fuel relative to the amount of air |
RE: OS 91FS needle settings
Thanks for the reply. I kind of thought thats where I should run it according to the performance, I just have heard from so many people that you don't want to run it too lean or you will spin the prop loose. I was continually trying to richen it according to doing a pinch test and I think it may have been rich enough to make it back fire, loosening the prop. This is my first 4-stroker and was wondering if the pump model would change anything while doing the pinch test. Thanks for the input.
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RE: OS 91FS needle settings
There may be a language problem?
Being rich does not make them backfire. Being lean makes them backfire |
RE: OS 91FS needle settings
LOL, no language problem. I don't know why my profile says Samoa. I understand that running them lean can cause back fire, but on the extemely rich side they can "hydraulic" and cause the prop to spin also. This happened to me as I was continually richening to try to get a base line. I was mainly trying to find out if pumped engines respond to the "pinch" test differently than a non-pumped engine, since this is the first I have owned. Thanks for the input.
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