ORIGINAL: doublesixes
ORIGINAL: BOUND_4_HELL
Hi doublesixes
I did the leaver adjustment to mine >> Things to be aware off >> be very careful with the little spring it is very squirmy and will zing out or your fingers fairly easy. I lost mine for about 5 minutes on one adjustment; I was lucky to find it. After that experience, I left the metering leaver and the spring attached to the carb base. I used two very tiny screwdrivers to bend the leaver into the correct position; you need to be very careful using the tiny screwdrivers, as you may damage the pop off needle, if you put too much pressure on it.
If you set the metering leaver too low you may run the float cavity dry and your engine will quit. Run it on the ground at full throttle for a couple of minutes to see if it will run without running out of gas, be careful not to overheat your engine.
Also do a spark plug test to see if you are running to lean.
Geppino
Geppino.
I was messing with the needles today and looks like I can lean the idle a bit and still have it reliable. It still burbles in the low/mid range but occasionally. I think I will continue fine tuning it tomorrow. One thing that I tried, is to let the engine idle at 1720 rpm for about 20 secs then throttle up in an instant. If there's no hesitation and instant response, then it most likely will behave OK in flight. If, on the other hand it shows the faintest sign of hesitation or responds slower than instant, the engine may quit in the air.
I fly a very light plane and I'd say that 30% of the time, my engine is idling because of my flying style so I'm at a higher risk of deadstick than pilots that run their engines in their mid to high ranges. I need instant response from idle since I'm doing (or trying) 3D stuff close to the deck. Fortunately I had all my flareups 2 mistakes high!
Hi doublesixes,
In my case I had a lot of midrange
miss-fires and burble, but the engine never quit. My Pitts is not 3D, but I do tumble it a lot. I do not think that running a little rich is going to harm the engine and if it keeps it from flaming out, you may want to leave things alone.
Here is a procedure that I have come across, for tuning the Walbro carbs, I'm not sure what four cycling is, so I have never tried it.
Geppino
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(1) The low end needle on a Walbro carb is ALWAYS the one closest to the engine, the high end needle is the closest one to the intake/choke.
(2) There is no fuel adjustment for idle fuel, only air feed set by the idle stop or servo.
(3) Both low end AND high end needles feed the top end fuel supply.
Let's tune up a Walbro:
Set the low end & high end needles to about 1 to 1 1/2 turns each.
Choke the carb or prime it, until the carb is wet.
Fire up the engine and let it warm up.
Let's set the top end first since it's the easier of the two.
Go to full throttle, and adjust the top end needle for peak RPM.
Leave it wide open for about a minute to see if it changes any.
Should the engine go lean, open the low end needle slightly, if this doesn't work... you will have to adjust the needle valve inside the carb.
If the top end runs OK, then slowly pull the throttle down until the engine begins to "four cycle" hold the throttle there.
Adjust the low end needle until the "four cycling" stops.
Now lower the throttle more until it "four cycles" again, and adjust the low end again.
Keep doing this until you reach full idle.
Now, from full idle begin to throttle up until the engine starts to bog or hesitate.
Open up the
HIGH END NEEDLE just enough to eliminate the bog or hesitation.
When this is done right, you will be able to set the throttle in any position and it won't four cycle, plus you will be able to transition from idle to full power without any hesitation at all.