55 AX vapor lock
#1
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55 AX vapor lock
Hi All,
I'm having a tough time adjusting this engine. It's never had a good transition. And a bunch of people with more experience than me have worked on it with out success. If I set the idle adjustment anywhere near what I thought was the factory setting, it vapor locks nearly every time. I need to turn the low-speed adjustment at least three turns to the left to get it to start without kicking off the prop.
-This is a profile plane with a side monted engone.
-I changed the entire fuel tank with all the plumbing
-The fuel tank is somewhat below the carb
- I can't see any sign of air bubbles
-Changed plugs without any change
-Changed fuel to a brand new gallon of 15%
I don't understand this. If I turn the idle screw to the right, I thought I was leaning out the engine. And I also thought that a vapor locked engine was a sign of flooding. So how could leaning out an engine cause vapor lock?
Thanks in advance
Mum
I'm having a tough time adjusting this engine. It's never had a good transition. And a bunch of people with more experience than me have worked on it with out success. If I set the idle adjustment anywhere near what I thought was the factory setting, it vapor locks nearly every time. I need to turn the low-speed adjustment at least three turns to the left to get it to start without kicking off the prop.
-This is a profile plane with a side monted engone.
-I changed the entire fuel tank with all the plumbing
-The fuel tank is somewhat below the carb
- I can't see any sign of air bubbles
-Changed plugs without any change
-Changed fuel to a brand new gallon of 15%
I don't understand this. If I turn the idle screw to the right, I thought I was leaning out the engine. And I also thought that a vapor locked engine was a sign of flooding. So how could leaning out an engine cause vapor lock?
Thanks in advance
Mum
#2
My Feedback: (11)
RE: 55 AX vapor lock
First off, we're not sure what you mean when you mention "vapor lock". Vapor lock happens on full-size engines when the engine compartment gets hot enough that the fuel in the fuel lines vaporizes and prevents the fuel pump from pushing liquid fuel. That is something that is just impossible in model engines. Model engines cannot get vapor lock.
If your engine is kicking off the propeller when you're trying to start it, then there are a few things wrong:
1) Prop nut is just not tight enough. We use a 6" wrench and actually use both arms to tighten as much as possible.
2) Engine is too rich or flooded. Flooded engines tend to backfire and kick back.
Start out with the settings recommended in the instructions and go from there. For new engines, it helps to start them at 1/4-1/3 throttle, since initial settings are on the rich side. Once the engine fires, you can open it up to full throttle for breakin running.
The idle mixture screw affects only the IDLE. You should not have to touch it at all until the high-speed needle setting is found. That will be after several tanks' worth of full-throttle running. Once the engine can be set to full throttle with the high-speed m ixture just rich of peak RPM, you can retard the throttle and then adjust the idle mixture. Likely, it will have to be leaned (turned clockwise).
You may wish to get an experienced modeler to help you with your engine operations.
If your engine is kicking off the propeller when you're trying to start it, then there are a few things wrong:
1) Prop nut is just not tight enough. We use a 6" wrench and actually use both arms to tighten as much as possible.
2) Engine is too rich or flooded. Flooded engines tend to backfire and kick back.
Start out with the settings recommended in the instructions and go from there. For new engines, it helps to start them at 1/4-1/3 throttle, since initial settings are on the rich side. Once the engine fires, you can open it up to full throttle for breakin running.
The idle mixture screw affects only the IDLE. You should not have to touch it at all until the high-speed needle setting is found. That will be after several tanks' worth of full-throttle running. Once the engine can be set to full throttle with the high-speed m ixture just rich of peak RPM, you can retard the throttle and then adjust the idle mixture. Likely, it will have to be leaned (turned clockwise).
You may wish to get an experienced modeler to help you with your engine operations.
#3
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RE: 55 AX vapor lock
Thanks Bill. I should have written hydraulic lock. Not vapor lock. I've had a bunch of people try to help me with this. The only way it will run at all is if the low speed idle is at least three turns out. If I try to go back to what I thought was the factory settings, the same darn thing happens.
Factory default is 1.5 turns out from the fully closed position... right?
Factory default is 1.5 turns out from the fully closed position... right?
#4
My Feedback: (11)
RE: 55 AX vapor lock
When you have just closed the throttle so that the opening is just closed, you gently turn the idle mixture screw clockwise unil it stops. Then back it out 1-1/2 turns. That's the starting point, and you adjust from there.
A model engine will hydraulic lock when liquid fuel gets into the cylinder and prevents it from turning. A running engine will usually not hydraulic lock unless much, much, too much fuel is getting into it. This could only happen at low throttle settings with the mixture setting being much too rich. If you lean it and the engine quits because it's not getting fuel, you cannot have hydraulic lock.
Also, an engine will usually get hydraulic lock only if the cylinder is pointed downward. If it's set up inverted, then you may need to add an on-board glow plug battery to keep the glow plug lit at low throttle settings.
A model engine will hydraulic lock when liquid fuel gets into the cylinder and prevents it from turning. A running engine will usually not hydraulic lock unless much, much, too much fuel is getting into it. This could only happen at low throttle settings with the mixture setting being much too rich. If you lean it and the engine quits because it's not getting fuel, you cannot have hydraulic lock.
Also, an engine will usually get hydraulic lock only if the cylinder is pointed downward. If it's set up inverted, then you may need to add an on-board glow plug battery to keep the glow plug lit at low throttle settings.