Pinch the Fuel Line
09-03-2002, 12:00 AM
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Pinch the Fuel Line
What does it mean when the fuel line is pinched and the engine speeds up? I have a Magnum XL 40A and it has no power at full throttle but when I pinch the fuel line off it increases power.
Thanx!
Mark
Thanx!
Mark
09-03-2002, 12:08 AM
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SOUNDS LIKE
Hi guy, it sounds like your way too rick , meaning your needle valve is turned out a bit too far.Next time you start your engine, go to full throttle, turn your needle clockwise , slowly, until your engine reaches full power (rpm's) then back it off until your engine looses aprox, 500 rpm's . see if it makes a diff. Buz^ PS you want to leave it a little rich as it will lean out in the air while flying
09-03-2002, 01:37 AM
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Pinch the Fuel Line
Buz thanx!
I found the problem, I had switched the fuel and muffler lines. I noticed surges of air going to the carb during the high speed run so I popped the top and behold. . . .I had the lines switched. Once I had these correctly placed the engine ran fine.
Thanx!
Mark
I found the problem, I had switched the fuel and muffler lines. I noticed surges of air going to the carb during the high speed run so I popped the top and behold. . . .I had the lines switched. Once I had these correctly placed the engine ran fine.
Thanx!
Mark
09-03-2002, 02:51 AM
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Re: Pinch the Fuel Line
Originally posted by Mdh4u
What does it mean when the fuel line is pinched and the engine speeds up? I have a Magnum XL 40A and it has no power at full throttle but when I pinch the fuel line off it increases power.
Thanx!
Mark
What does it mean when the fuel line is pinched and the engine speeds up? I have a Magnum XL 40A and it has no power at full throttle but when I pinch the fuel line off it increases power.
Thanx!
Mark
HI Mark, If you are interested.. I use the old pinch the line to set my engines needle.
I start the engine and pinch the line , if the engine speeds up it is to rich..adjust ..pinch until the engine does not speed up and back off the needle a click or two and pinch line again if ir speeds up slightly you should be good and the engine will not go lean on you in the air.
George
TAKEOFF IS OPTIONAL....LANDING IS MANDATORY!!!
09-03-2002, 03:24 AM
#5
Pinch the Fuel Line
Hi all, the pinch test is a good method to check fuel setting. Does anyone know how this method was developed ( a bit of history), what is the theory behind it, and why does it correlate to actual in-flight conditions i.e. what is the equivalent phenomenon to "pinching" during flight ? I can't think of anything that is tantamount to a "pinch" during flight apart from a clogged fuel tubing. Cheers..........
09-03-2002, 10:34 AM
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Pinch the Fuel Line
Despite what you may read here the "Pinch" method of setting a needle is bad practice. The continual bursts of high revs and lean fuel amount can overheat the engine before the optimum needle setting is reached. Too often I see an overheated engine but the "Pincher" has not realised it. He still pinches and screws with the needle to no avail. The engine is overheated and will not come up. The engine has to be cooled and the process started again.
This time do it properly, with a Tach and bring the engine up to max revs slowly.
Ed S
This time do it properly, with a Tach and bring the engine up to max revs slowly.
Ed S
09-03-2002, 11:42 AM
#7
Pinch the Fuel Line
HERE IS A LOW END PIECE.---I use to use the pinch method until I started reading the fine print. If I use it by accident, it is only part of a couple other back ups. If you get a slight in increase, your on the lean side. If it engine quits, your to rich. I actually prefer no change in RPM. Be that as it may.---LOW END ADJUSTMENT- Tune it as you see fit. Then disconnect the fuel line from the carb nipple (if you can). If the rpm increases before the engine quits, your "low end" is to rich. If the engine just dies, your low end is to lean. I go for a very slight increase. I have been using this "Manual Method" for about a year and my engines run perfect.
09-04-2002, 01:56 AM
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Pinch the Fuel Line
Well you guys may be right as I have only been doing this for a while. I think that my best enging is and old K&B 61 that I have been flying for about oh 10..15 years and I must be doing something right as the old dog still pulls my 6.5 # stick straight up. It can't all be luck! But I am sure you folks know best. I do have a tach and cross check it with my pinch setting. I don,t think I said that the pinch was the only way. What would you do wtihout the modern tools for tweeking your engines? I started pinching the fuel line back in oh..1950 or so with my control line and free flignt. Try the old methods guys .....your battery may go dead at a critical moment on those electronic aids ! LOLOLOL. What would you do with out an electric starter??
I am not being a wise guy, some of you folks are quick to jump on someone without giving thought to what was said.
GEF
GRAVITY.....NOOO, EARTH SUCKS!!!
I am not being a wise guy, some of you folks are quick to jump on someone without giving thought to what was said.
GEF
GRAVITY.....NOOO, EARTH SUCKS!!!
09-04-2002, 02:29 AM
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Pinch the Fuel Line
Oops, I did just what I was saying not to do . Please accept my apologies one and all.
Cyclic, I like your method and will try it. Does that way improve idle, transition....?
I,ve always found that the engine speeds up when you remove fuel line from carb inlet. The engine is starved for fuel and goes lean for a sec or two. Is this true the way you do the adjusting?
Never to old to learn !
Thanks
GEF
Down is still up even if you stand on your head
Cyclic, I like your method and will try it. Does that way improve idle, transition....?
I,ve always found that the engine speeds up when you remove fuel line from carb inlet. The engine is starved for fuel and goes lean for a sec or two. Is this true the way you do the adjusting?
Never to old to learn !
Thanks
GEF
Down is still up even if you stand on your head
09-04-2002, 10:51 AM
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newbie...but I like it
As I am on a budget and farly new with this hobby, I don't have a tach yet. I use the pinch test before each day of flying.
As for how it works, it is alaogous to screwing IN the needle valve in a "pinch". If the engine is getting too much fuel (rich), the RPMs increase. Conversely, if the engine DIES, it is starved for fuel and you are lean.
Because the relative pressure caused by muffler back pressure and the difference in fuel level from carb (like a siphoning effect) decreases as the flight continues, slightly less fuel gets to the engine as the tank gets empty. The efective result is that the engine leans during flight. Thus, always start you flight 1-3 clicks on the rich side of a "no change" result from a pinch test.
Zee
And yes....I do need a tach, and I think that is more accurate than a pinch test.
One more thing....you have to return your engine to idle between each successive pinches in order to have this test work right.
As for how it works, it is alaogous to screwing IN the needle valve in a "pinch". If the engine is getting too much fuel (rich), the RPMs increase. Conversely, if the engine DIES, it is starved for fuel and you are lean.
Because the relative pressure caused by muffler back pressure and the difference in fuel level from carb (like a siphoning effect) decreases as the flight continues, slightly less fuel gets to the engine as the tank gets empty. The efective result is that the engine leans during flight. Thus, always start you flight 1-3 clicks on the rich side of a "no change" result from a pinch test.
Zee
And yes....I do need a tach, and I think that is more accurate than a pinch test.
One more thing....you have to return your engine to idle between each successive pinches in order to have this test work right.
09-04-2002, 06:33 PM
#12
Pinch the Fuel Line
[QUOTE]Originally posted by Sky-jacker
[B]Oops, I did just what I was saying not to do . Please accept my apologies one and all.
Cyclic, I like your method and will try it. Does that way improve idle, transition....?
Frankly everything runs fine. Transition and the whole thing. Around here I notice that those who rely solely on the pinch are trying to squeze every last rpm out of it and that can cause problems most of which are glow plugs. I do a pinch and go for no change, then disconnect it and listen for a slight rise for the low end. Not a big rise but a slight.You may want to lean your low end on purpose to here the difference.
[B]Oops, I did just what I was saying not to do . Please accept my apologies one and all.
Cyclic, I like your method and will try it. Does that way improve idle, transition....?
Frankly everything runs fine. Transition and the whole thing. Around here I notice that those who rely solely on the pinch are trying to squeze every last rpm out of it and that can cause problems most of which are glow plugs. I do a pinch and go for no change, then disconnect it and listen for a slight rise for the low end. Not a big rise but a slight.You may want to lean your low end on purpose to here the difference.
09-04-2002, 06:36 PM
#13
Re: newbie...but I like it
Originally posted by FlyingZee
As I am on a budget and farly new with this hobby, I don't have a tach yet. I use the pinch test before each day of flying.
As for how it works, it is alaogous to screwing IN the needle valve in a "pinch". If the engine is getting too much fuel (rich), the RPMs increase. Conversely, if the engine DIES, it is starved for fuel and you are lean.
Because the relative pressure caused by muffler back pressure and the difference in fuel level from carb (like a siphoning effect) decreases as the flight continues, slightly less fuel gets to the engine as the tank gets empty. The efective result is that the engine leans during flight. Thus, always start you flight 1-3 clicks on the rich side of a "no change" result from a pinch test.
Zee
And yes....I do need a tach, and I think that is more accurate than a pinch test.
Huh?
One more thing....you have to return your engine to idle between each successive pinches in order to have this test work right.
As I am on a budget and farly new with this hobby, I don't have a tach yet. I use the pinch test before each day of flying.
As for how it works, it is alaogous to screwing IN the needle valve in a "pinch". If the engine is getting too much fuel (rich), the RPMs increase. Conversely, if the engine DIES, it is starved for fuel and you are lean.
Because the relative pressure caused by muffler back pressure and the difference in fuel level from carb (like a siphoning effect) decreases as the flight continues, slightly less fuel gets to the engine as the tank gets empty. The efective result is that the engine leans during flight. Thus, always start you flight 1-3 clicks on the rich side of a "no change" result from a pinch test.
Zee
And yes....I do need a tach, and I think that is more accurate than a pinch test.
Huh?
One more thing....you have to return your engine to idle between each successive pinches in order to have this test work right.
