I was wondering if anyone could help me out with some engine troubles that I have been having. I recently completed my first build (Kadet LT 40) and I put a .40 FX engine on this airplane. The engine develops good power, but the problems occur at mid to low throttle. WHen I advance the throttle, the engine really loads up, and behaves as if it is a full turn on the needle valve too rich. Full throttle is okay, after it leans out, and when I return to a lower throttle setting, the engine runs superbly, untill landing. THe engine has a disturbing tendency to quit. I think only 2 or 3 flights have seen the engine runnign after landing.

I think the fuel tank is in the right place, it is where it is placed as per sig's directions. I do have a "t" for filling the fuel tank and a filter between the engine and the fuel tank, though.

I do not have any experience on how to tune an aircraft engine for proper operation, please give me any help you can.

You dont need the t get rid of it but you do have the filler line plugged air tight right? if you stick your finger in the exhaust right behind the muffler you should have some fuel residue on your finger if you dont richen it up if its drippin lean it some i think your a tad too rich get with someone at your club to help you tune
good luck

ashley95, I think his trouble hes having may be due to his low end setting?
if its at idle and he slaps the throttle and it falls on its face then i would start by turning in the low end a notch or two or vise versa until he has a smooth transition. if his settings on the low end are correct he can tell by pinching the fuel line and the motor should raise the rpms by 2-300 and then stall not carry on.that would tell me hes to rich on the low end?

my self and a few others all had the same trouble on our new nexstars out of the box a couple years back


KE7EHA,I you dont see any air bubbles in the fuel line when the motor is running then there should be no trouble within the fuel system at all

You can get rid of the T, it lends itself to adding to potential leaks in the future, in not presently. Simply pull the fuel line off the needle valve assy and pump the fuel to the tank from there,,,,,between filter and tank. Im not sure, but there should be a needle adjustment in the center of the throttle arm. that would be the low end adjustment. At least on the 46 AX and ST GS40 it is. turn it in 1/8 of a turn nothing more. Start and run it. If the problem remains or worsens, such as it not starting at all. Turn it out 1/4 turn, then try again,,,use baby steps. It will work its way out.

Low end is rich. It's loading up and can't clear itself out quickly when you throttle up.

Dr.1

Idle mixture too rich is correct. OS ships most of their engines this way as a safety feature to avoid new pilots burning them up. Turn the "idle" adjuster in 1/8 turn increments until the engine will accelerate properly. Retuning of high speed needle may also be needed when done. Once you get the idle mixture figured out. you shouldn't need to mess with it again unless there is a MAJOR atmospheric change.

DR1 & Bruce have it right.

As the others have said....

The low end is too rich. Unburned fuel is accumulating in the crankcase. As you speed the engine up, the fuel tries to come up into the combustion chamber.

Enjoy,

Jim

I agree w/ the other fellas about the low speed mixture being set too rich. Be careful to not go too lean, it's easy to go to far w/this screw as the sweet spot on this needle is quite small. Run the engine between each adjustment you make and bring the throttle up to full power quickly and consistently. If you get into trouble, OS does provide a default setting for the low speed needle in their engine manuals and I think you can get these manuals in PDF either at tower or the osengine home page. Good luck and mind your fingers.

If you get the idle too lean, the engine will not take the throttle. The high speed needle will be ineffective.

Enjoy,

Jim

One other minor point, make sure you are not trying idle the engine at too low RPM's. 2000 RPM's at idle isn't bad; any lower might be a cause of the engine quitting.

DaveB

I re-tuned my engine on the bench recently. As was suggested, I needed to lean down the idle mix a bit, causing smooth transitions. Havne't yet had time to fly [college student] but I'm optimistic. However, the carb screws vibrated loose and fell to the ground. Anybody have any reasons for this? I'm probably going to use lockwasher/nut and locktite for the next set of screws.

The 40-46FX tend to loose the idle speed screw if it is out the least bit too far.

Also, sometimes, if the throttle barrel comes out, the barrel spring will go down through the engine causing substantual damage.

Hi there all,

I have been using Evolution's .45 engine which came with P51 Mustang PTS. Engine has never given me trouble, but now a days, its giving me trouble, 3 times during flight it shut off/dead stick, and even now its giving me hard time to start, as it always starts with chicken stick with no trouble. I experienced the dead stick last sunday, before that, it never gave me that problem, but during inverted flight it flew ok, by the time I turned it straight, engine shut off, what could be the problem? I remember that I was using the fuel which turned little black due to sucking back the unused fuel from the airplane, with that fuel it never gave me trouble, but as I started using clean new fuel without any residue, it started giving me trouble, please help me, what can I do to fix that problem.

Thanks

Mody

Maybe the weather is turning a little cooler and you need to richen the needle a little?

Thanks w8ye,

Well, you are right weather is getting cooler, but in the day time its little hot, but in order to richen the fuel, where should I turn the needle, clockwise or anti-clockwise?

Mody

Anti-clockwise a couple clicks until you get it right.

You may run out of adjusting travel on that model engine. If you do, get back on here or the glow engine forum and find out how to readjust the limiting collars