lioneltamara

hello everyone.i have a .46 la engine that only provides me with dead stick landings.the motor runs great on the ground and in the air until i idle back for my approch.then it just shuts down. my instructor has tunen the engine to the best he can.he also tells me that this engine(os .46 la)does not have a reliable idle anyway.is this true or false.a dead stick landing is a very hard way to learn .as i am new to the hobby i am still learning.i have 25 short flights with 16 take offs and 12 landings,and 1 face plant.

Hobbsy

My Feedback: (102)

Is the airbleed screw about halfway across the air inlet hole mine is slightly more than halfway across that is more than half closed. My guess that airbleed is too far open therefore too lean.

w8ye

My Feedback: (16)

You may try increasing the idle speed a little with the trim on your transmitter?

Dsegal

Be sure that the backplate screws are tight.

bkdavy

My Feedback: (1)

My OS 46 LA has a wonderfully reliable idle at about 2500 rpm with an 11x5 APC prop and an OS A3 glow plug. If you follow the directions in the manual for tuning, you'll get very close. The key is to remember that it is an airbleed carb. Turning the air bleed screw counter-clockwise opens the air-bled hole further and leans the low end mix. Make the adjustments slowly (1/4 turn or less). Then retune the high end to 200-500 RPM below peak (to the rich side on the high end needle). Use a tachometer. Its much more reliable and repeatable than just tuning by ear. Then idle it down, setting your trim settings to maintain a reliable idle between 2500 and 3000 rpm, wait about 10 seconds, then push it quickly to full throttle. The engine should transition smoothly. If it sputters then runs up, the low end is too rich. Open the air-bleed screw another 1/4 turn, retune the high end and try again. I've found that the low end can be a little lean, as long as the high end is slightly rich. You must retune the high end everytime you adjust the low end. In my experience, an overly rich high end needle will cause the low end to look rich as well. As your tuning gets closer to optimum, you'll find the reliable low idle rpms will also drop until your in the 2500 rpm range.

Good Luck

NM2K

My Feedback: (14)

Yep, this is a big problem with two-stroke engines equipped with plastic backplates.

Ed Cregger

piper_chuck

My Feedback: (12)

This is what I posted in the other thread you opened for this problem:

The LA engines are fine. They're not high powered engines, but properly adjusted, they run fine. Unfortunately, what often happens is that an engine series gets a bad reputation and people use this as an excuse when they don't adjust it correctly. This summer I helped 2 different people sort out engines that were known to be "troublesome" and which others had given up on. In both cases, the root cause was the glow plug. Once I put in a good plug we were able to get them running flawlessly.

If yours is stalling when you throttle back, something is not adjusted correctly. The problem could be:
1) Idle airbleed screw not adjusted right.
2) Wrong or bad glow plug. I like OS #8 for general sport flying.
3) Attempting to idle it too low.
4) Bad fuel.
5) Waiting too long to land, so the fuel is too low in the tank.

You've got to get the engine running well on the ground. Make sure it will idle for 30-45 seconds and then power back up with minimal hesitation. Try doing this with the tank 1/4 full and see what happens. Be sure the high speed needle is not too lean or rich. Don't rely on the "pinch test", it's not accurate. Set the high speed needle to where you think is right. Then get a firm grip on the plane and point the nose straight up. If the engine slows immediately, it's too lean. Lower the nose and set it richer. If the engine speed doesn't change, or gradually slows, it's also too lean. If the engine speeds up a little and then holds this speed (you want to keep it pointed up for at least 5-10 seconds), the needle is just about right. If the engine speeds up significantly, the needle is too rich.

Once you've got the high speed needle set right you can begin working with the air bleed screw. One of the best tips I ever learned for getting the low speed idle mixture close to correct is to start the engine and leave the glow connector attached. Run the engine up to full to clear out the carb and then back to idle. Let it idle for 5-10 seconds and then remove the glow connector. If the engine slows significantly, it's too rich. If the engine slows a little, it's just about right. If the engine speed doesn't change at all, it could be right, but it's possibly too lean. Once it's close to correct, remove the glow connector and let it idle for a good 30 seconds and then bring it quickly up to full throttle. If the engine immediately dies, it's probably too lean. If it stumbles and spits fuel out the muffler, but eventually starts speeding up, it's probably too rich.

And finally, a note about the carb types. The LA series has an air bleed carb for controlling idle mixture. Many other engines have a second low speed needle. The air bleed carbs have a small hole in the front of the carb that lets in a bit of air when the throttle is nearly closed. There is a screw that can be used to control how much of this hole is open. When you turn the screw in the hole is smaller, which lets less air in. This gives you a richer idle mixture. Turning the screw out opens the hole and allows more air in. This gives you a leaner mixture. Some people say air bleed carbs don't work well, but I've always had good luck with them. One of the planes I fly has a Thunder Tiger GP-15 on it. The engine starts with a couple flips, idles perfectly, transitions to full without stumbling, and shuts off when I tell it to. Can't ask for more than this.

RC-Captain

guess I was right after all. watch the responses pour in ......GL with your engine