ORIGINAL: armody
Hi there all,
I've been observing eversince I'd been flying with our senior old flying friend as he has 2 airplanes one is 25 or 30 size other one is 40 size. One is low winger and has .30 O.S. Engine and other one is high winger with O.S. 46 engine in it. The plane with .46 size engine has muffler nipple leaky, it leaks the fuel all the time durning flying. Sometimes it does give dead sticks but it really flies despite of that fault.
Leaky pressure fittings will provide you dead-stick practice.
You may set a needle valve to run OK with a reduced pressure, and some engines may not need the pressure at all, depending on the Carb. opening size. In any case if the needle is set with pressure available, then reducing that pressure will lean the engine and maybe cause the flame-out.
When you come to idle on your engine, observe the fuel line connecting the muffler to the tank. You will observe almost NO airflow into the tank, even unto sometimes a drawing from the tank. The engine at idle is usually running on venturi action vice pressure during idle. With leaks in the nipple, when you advance the throttle, with lower fuel levels, there is inadequate air pressure build-up in the tank to provide the increase in fuel flow for high-speed. Thus another flame-out practice, but hey, this one ain't just practice!!
Place a gasket of some sort under the nipple and tighten it down.
Little low winger plane has carb needle leaky, high speed needle but it does fly good with good rpms and few times it gave us dead stick. Both planes I fly and they fly well, my question is, do these factors make any difference in engine's performance or not and as I didnt experience much problem with those engines, could it be a coincidence they kept running or should this problem be fixed?
Please suggest and advise from your past experiences if you had gone thru
Thanks
Mody
A leaky needle valve usually needs a new O-ring or a tightening of the holding nut as in old Super Tigres. HOWEVER it is easier to follow this:
I NEVER trust a needle valve so I always slip some fuel tubing over the NV and the screw-in area. That seals off the leaky problem, stops the air/fuel leaks so you can get a good needle setting and usually makes your problems mostly all go away.
Sometimes I actually use two sizes of fuel line, one over the other to secure a stop-leak. Makes life easier and you don't have to cuss so much!