Debra
01-08-2007, 07:49 PM
I have a SuperTigre 2300 2-stoke engine. I'm running the engine on a bench for tuning purposes with a Slimline Inverted Pitts muffler using "LARGE" fuel tubing and a "STANDARD" fuel tank with included hardware. I started the engine using the factory carburetor settings... IDLE 4 3/4 and HIGH SPEED 2 1/2. The engine ran great up to mid throttle where it dies. Then enriching the High Speed Needle (HSN) one turn until the engine ran with the carb full open, which was about 4 turns. Now I have the HSN 7-8 turns rich and there's no change in RPM from mid throttle to full throttle. Still when I do the "pinch test" the engine dies without running up in RPM, meaning its still running lean. The only thing I haven't done yet is run fuel directly from the fuel can to the engine.
Why is the engine not receiving enough fuel?
Should a large 2-stroke engine run and tune like a small 2-stoke engine?
Is it best to run the engine at full throttle or idle for break-in?
Directions say full throttle..
Rob, Waupaca, WI
Dear Rob,
If you have to back your S.T. needlevalve out 7~turns and can't get the engine to run rich, something is obstruction the fuel flow. Remove the high speed needle and flush the system. Foreign matter may be clogging the fuel passage. If this doesn't help try backing out the idle needlevalve. It could be screwed in too far and not withdrawing from the high speed jet as the throttle is advanced. If the problem still persists, it might be the clunk in your fuel tank, i.e., the hole too small. It should be the same as the large fuel line you are using. If using one of the sintered bronze clunks it could be clogged with congealed oil so replace it. The tank probably has a piece of 1/8" tubing in the outlet, Increase this to 5/32" tubing.
If using a filter between the tank and carburetor make sure it has large enough inlet and outlets holes and is not plugged. Also, the carburetor is designed to work with muffler pressure, so be sure you are using it and the pressure nipple is not plugged up. I would appreciate hearing what you find.
The engine should be run at full throttle during break-in so that it comes up to operating temperature. Lean the engine in so that it is running in a slightly rich two cycle and then richen back up again with the needlevalve. Repeat the leaning/ richening procedure allowing the engine to run longer when leaned each time for the first tank or two of fuel. Then install it in your aircraft and run it in a very rich 2-cycle the first flight. 2nd flight, the equivalent of a click or two leaner, By the 6th or 7th flight you. want to be running the engine in a slightly rich 2-cycle. If your flying ability permits,
make big loops, Cuban Eights, etc. The engine will break in faster by making it work. Be careful about any lean runs during the break-in which can permanently damage the engine. Good flying.
Clarence Lee
Why is the engine not receiving enough fuel?
Should a large 2-stroke engine run and tune like a small 2-stoke engine?
Is it best to run the engine at full throttle or idle for break-in?
Directions say full throttle..
Rob, Waupaca, WI
Dear Rob,
If you have to back your S.T. needlevalve out 7~turns and can't get the engine to run rich, something is obstruction the fuel flow. Remove the high speed needle and flush the system. Foreign matter may be clogging the fuel passage. If this doesn't help try backing out the idle needlevalve. It could be screwed in too far and not withdrawing from the high speed jet as the throttle is advanced. If the problem still persists, it might be the clunk in your fuel tank, i.e., the hole too small. It should be the same as the large fuel line you are using. If using one of the sintered bronze clunks it could be clogged with congealed oil so replace it. The tank probably has a piece of 1/8" tubing in the outlet, Increase this to 5/32" tubing.
If using a filter between the tank and carburetor make sure it has large enough inlet and outlets holes and is not plugged. Also, the carburetor is designed to work with muffler pressure, so be sure you are using it and the pressure nipple is not plugged up. I would appreciate hearing what you find.
The engine should be run at full throttle during break-in so that it comes up to operating temperature. Lean the engine in so that it is running in a slightly rich two cycle and then richen back up again with the needlevalve. Repeat the leaning/ richening procedure allowing the engine to run longer when leaned each time for the first tank or two of fuel. Then install it in your aircraft and run it in a very rich 2-cycle the first flight. 2nd flight, the equivalent of a click or two leaner, By the 6th or 7th flight you. want to be running the engine in a slightly rich 2-cycle. If your flying ability permits,
make big loops, Cuban Eights, etc. The engine will break in faster by making it work. Be careful about any lean runs during the break-in which can permanently damage the engine. Good flying.
Clarence Lee