Gas engine tuning for newbies....

[bob_nj]

Understood!
I guess my view is that it will be very difficult to get to (cowling), nevermind reach my giant engine's fuel line.
Second point is that I didn't know that method worked for the types of carbs and fuel delivery systems on a gasser?

Let's see what others say...

[mfuess]

	Quote: Originally Posted by bob_nj
	Understood! I guess my view is that it will be very difficult to get to (cowling), nevermind reach my giant engine's fuel line. Second point is that I didn't know that method worked for the types of carbs and fuel delivery systems on a gasser? Let's see what others say...

NO. Gassers are not GLOW engines and you don't tune them as though they are.

[bob_nj]

mfeuss --> Does that mean you agree that the method is for glo mentioned in the book?

[rcign]

Generally works the same, except a gasser carb has fuel in a chamber under the diaphragm, and it takes a while to burn off enough fuel to tell it it's rich or not...
Try it some time, take the fuel line off the carb and see how long it takes to die...

[jfassino]

	Quote: Originally Posted by mfuess
	NO. Gassers are not GLOW engines and you don't tune them as though they are.

mfuess,

Great thread, could you share why tis does not work..It is always easier for me if I can understand why? Is the carb the issue?

Thanks for all of your comments and help.

Jim

[mfuess]

Glow engines use exhaust pressure to supply fuel to the carb. As the fuel level changes, so does the available pressure to the carb. So the tune changes as the fuel level drops. Because of this, you have to run a glow engine slightly on the rich side. Gas engines on the other hand, use a fuel pump to supply gas to the carb. Fuel pumps maintain constant pressure regardless of fuel level so the carb doesn't see any fuel level change, thereby the tune doesn't change.

To give you an idea of how effective a pump is, I bench ran a 45cc gas engine with the gas tank resting on the floor. It was a 4 foot drop below the engine and about 5 feet of fuel line. The engine ran perfectly as it always did. Try that with a glow engine and it won't even start.

[jfassino]

mfuess,

Thanks for your reply, and again thanks for a very usefull tuning process.

Jim

[Albatross]

mfuess

Question for you:

BME 110, burbles and hesitates just at the moment when I open the throttle during take off.
I can avoid this hesitation If I do a WOT for only one second just prior to heading to the runway.

I already installed a line going from the diaphragm to the fuselage.

Once in the air, behaves OK. However would hear that "4 strokes" sound when going from high to low.
The needles of this engine seem to be very sensitive.
The engine should have 8 gallons.
I am running this engine on a Boly 27x10.
I am planning to install a mejzlik 27X10.
Flying at 5700 ft ASL.

[Pro1Foam]

Sounds to me your low end maybe a bit rich and/or you have fuel build up on your reed valves. I always do a full throttle rev up just before take off to get rid of any fuel build up on the reeds. My2c

[Albatross]

Thanks
That’s most likely right; the side effect of reducing closing the low end needle is that firing up the engine from cold is somewhat difficult.

Now if I let the low end without touching it, while doing 3D at low rpm, then if I want to open the throttle, saying to go on a vertical maneuver or simply switching to normal flying style, then that hesitation comes along.

May be out of the context, however is just more information about how this engine behaves: I got a dead stick while flying low inverted and at low rpm … needles to say that under such flying attitude all I could do was a controlled crash.

By now the airplane is fixed and ready to go, carburetor cleaned. Gas tank clunk checked out.
I hope for the best next time I take her to the field.

[Pro1Foam]

Do the tuning method in the first post of the thread and your probllem will go away. (Your low end is rich).

What oil are you useing?

[mfuess]

	Quote: Originally Posted by Albatross
	mfuess Question for you: BME 110, burbles and hesitates just at the moment when I open the throttle during take off. I can avoid this hesitation If I do a WOT for only one second just prior to heading to the runway. I already installed a line going from the diaphragm to the fuselage. Once in the air, behaves OK. However would hear that "4 strokes" sound when going from high to low. The needles of this engine seem to be very sensitive. The engine should have 8 gallons. I am running this engine on a Boly 27x10. I am planning to install a mejzlik 27X10. Flying at 5700 ft ASL.

You're slightly rich on the LOW needle. Sensitive needles "generally" indicates a heavy load. (heavy prop) But it shouldn't be a problem though... BME 110 is a very potent engine.