DownSideUp

My os40LA has been run-in properly. I followed the directions explicitly. It ran well for about 5-10 flights then I started to have problems. I'm experiencing the engine quitting when I rev it to high rpms. If I back it down before it quits, it will run fine. Then as I raise the rpms again, it wants to quit again, and will if I don't back it off. It cost me a super sportster at my flying field today, when I couldn't manage to dead stick land. It doesn't happen all the time. About 1 out of every three flights. When I run it on the ground before flying, it never happens. I can however get the problem to occur on the ground after it has happened in the air.

I have done the following to try to fix the problem:

1) Checked all fuel lines for leaks.

2) Run fuel through my needle valve, cleaned the engine, fuel lines, carb, and fuel tank.

3) Balanced my prop

4) changed my glowplug

5) Put a fuel filter on my hose sucking fuel from my container, and put a filter on the hose before the needle valve.

I don't know what else to do, and no one I have talked to has any solutions other than the ones I have given above. Thanks for any suggestions you may have.

RCLIVIN

My Feedback: (46)

I have an la46 with similar problems, I heard someone say to pull the carb off & use some type of rtv silicone around the base of the carb & put it back together, let dry & try it. I will try this when I get home.

Gil

DownSideUp

How often does this happen with your 46? And if there is something wrong with the carb, wouldn't it happen all the time?

RCLIVIN

My Feedback: (46)

On mine, it seems to run great on the ground & after runing wide open for 2-3 minutes it starts to slow down loosing power until you land or go dead stick.

Gil

Bax

My Feedback: (11)

Is sounds like the engine's going lean in the air. If the engine will run all day on the ground with no problems, it's not the engine. The problem is somewhere else.

If the engine won't have any difficulties until it's happened in the air, then the likely overheat has caused a bad piston/cylinder fit. That can only be repaired with a new piston/cylinder assembly.

Vibration-induced fuel foaming is the most common cause of the difficulty you're describing. Usually, the engine will tend to go lean in a certaim RPM range, where vibrations to the fuel tank are maximized.

It's possible this happened on a earlier flight and now the engine's had enough damage that it will lose compression when it warms up and will then lose power.

You can send the engine for service to see if there's anything wrong it it.

flytheedge

My Feedback: (84)

What kind of glow plug are you using? I prefer the Thunderbolt brand.
Clint

cwat212

Sounds like it is too lean. Have you checked the needle valve setting on the ground by pointing the nose up at full throttle?

jdg_rit

What is the nose up check? Thanks.

Jarodd

cwat212

At full throttle, carefully while holding the plane, tilt the nose of the plane so that it is pointing staight up. If the engine is adjusted too lean the engine will quit. If the engine quits, turn the needle valve out a little and try again.

Very simple way to check if the engine setting is too lean.

jdg_rit

So if the engine doesn't change it is set correctly? Thanks.

Jarodd

cwat212

It just makes sure your needle is not set too lean. It helps to check that the engine will not quit in the air do to a lean needle setting.


adjust the needle valve on the ground to reach the max rpms - Then back the needle out about a 1/4 turn to slightly richen. Then tilt nose up to make sure it does not quit running.


An engine should run a little rich on the ground because the engine will lean out a little in the air. It is always better to be a little rich than too lean.

This is just a simple way to adjust and check the high end needle.

This is only after an engine is broken in. Use a extra rich setting until the engine is properly broken in.

RCToon

I have a LA40 and after tuning the engine perfectly on the ground it used to die off just as the model lifts off the ground (yes, it was running rich on the ground, so its not a leaning out issue). After fiddling with the carb, fuel, glowplugs for days the problem just died out when I tightened the backplate a qtr turn each screw.
I think what happens is when the engine runs on ground the prop pulls the shaft in front and there is no pressure on the back plate. But once the aircraft moves the prop and shaft move back pushing the backplate causing the backplate to move so slightly that an air leak occurs and the engine dies.
I dont know if I am correct about the analysis, but this has been my experience.

Bax

My Feedback: (11)

Time to close this thread. It's gotten beyond the manufacturer support phase. Please continue it in general discussion, if you wish.