Help!! Engine Problems
06-28-2003 | 12:46 AM
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From: Minot AFB, ND
Help!! Engine Problems
I have a brand new Tower Hobbies .75 I can not get it started for the life of me! I would just love to break it in and get my plane in the air, but I can get it to run. I have tried adjusting both the high and low ends with no luck. Every no and then it will fire up and run for about 30sec. and quit. Can someone please help? I'm up for any suggestions.
06-28-2003 | 03:26 AM
#4
Help!! Engine Problems
In the absence of the "scoop"
Let's just start from scratch.
*re-read the instructions.
*Fresh fuel
*charged glo starter.
*Open the main needle valve 2 or 3 turns
*set the throttle so it is just slightly open.
Start the motor...leave the glo starter attached.
Advance the throttle to full....and SLOWLY turn in the main needle valve until you hear a definite pitch change in the sound of the engine...it'll go from a rough 4C operation to a "scream".
STOP RIGHT AT THAT POINT...DON'T LEAN IT ANOTHER CLICK.
Allow the motor to run at the richest (most open) needle valve setting that will keep it screaming. Make this adjustment with the throttle WIDE OPEN.
Allow the motor to run for about a minute. Stop it by closing the throttle...don't pull the fuel line or anything else.
Allow the motor to cool completely...then run the motor again (needle should be OK)
Repeat the run/cool process 8-10 times. I don't care who doesn't like it...it's the right way to do it.
After this...extend the running time a bit and lean the needle a bit more. If the motor "sags" (ie: loses power) you've gone too lean...richen it back up right away!
When the engine will hold a fulll song scream for a minute or so...go fly. Keep the needle set 2-300 rpm below peak and you should be fine.
Let's just start from scratch.
*re-read the instructions.
*Fresh fuel
*charged glo starter.
*Open the main needle valve 2 or 3 turns
*set the throttle so it is just slightly open.
Start the motor...leave the glo starter attached.
Advance the throttle to full....and SLOWLY turn in the main needle valve until you hear a definite pitch change in the sound of the engine...it'll go from a rough 4C operation to a "scream".
STOP RIGHT AT THAT POINT...DON'T LEAN IT ANOTHER CLICK.
Allow the motor to run at the richest (most open) needle valve setting that will keep it screaming. Make this adjustment with the throttle WIDE OPEN.
Allow the motor to run for about a minute. Stop it by closing the throttle...don't pull the fuel line or anything else.
Allow the motor to cool completely...then run the motor again (needle should be OK)
Repeat the run/cool process 8-10 times. I don't care who doesn't like it...it's the right way to do it.
After this...extend the running time a bit and lean the needle a bit more. If the motor "sags" (ie: loses power) you've gone too lean...richen it back up right away!
When the engine will hold a fulll song scream for a minute or so...go fly. Keep the needle set 2-300 rpm below peak and you should be fine.
06-28-2003 | 01:18 PM
#5
My Feedback: (8)
Help!! Engine Problems
The engine runs so it must be a fuel/air delivery problem. It can be in the carb needle settings, the fuel lines to the engine (possibly reversed), or the fuel line/clunk in the fuel tank.
Try resetting your low end needle. Open carb to about 1/4 throttle setting. Turn high end needle about 5 turns from closed. Open carb to full throttle and use a clean piece of fuel tubing attached to the carb and blow into it with your mouth. This ensures your high end needle is allowing fuel (in this case air) to flow into the carb. If it doesn't, than try another turn out or finding the obstruction.
Once you've verified the high end needle valve is working properly and allows air to be blown into the carb at full throttle, now (keep the same high end needle setting 5-6 turns out) and close throttle to about 1/4 throttle setting. Turn low end needle valve so it is completely seated (meaning closed byturning it clockwise, do this gently and don't force anything). Now with the carb opened at 1/4 throttle setting, SLOWLY rotate the low end needle valve counterclockwise (to richen the low end mixture) while simultaneously trying to blow air into the carb through the clean fuel tubing. Stop richening the low end needle valve when you first "feel" (more accurate) or hear air leaking into the carb.
Now, return to high end needle valve and close it completely and open it about 2 1/2 turns from closed. Recheck to make sure this 2 1/2 turn setting allows air to flow into carb and double check the low end needle setting to see if you can blow air into it with carb at 1/4 throttle setting. If all checks out, then attached fuel tank line to engine, prime engine manually with engine at full throttle, return to slightly less than 1/4 throttle, attached glow driver and start with starter.
As soon as it fires up, don't touch anything. Leave glow driver on and let engine warm up for about 30 seconds. Now with glow driver still on, slowly advance throttle setting. You should be able to get it to full throttle. If it dies from going from 1/4 to 1/2 throttle and above (with glow attached) it probably means you are too lean on the low end needle valve. Just open it (low end needle valve) up a little bit (about an 1/8 of a turn or less). Repeat as necessary until engine can advance above 1/2 throttle without dying. Once it can run at 1/2 and above, remove glow driver and go to full throttle. At full throttle, lean out high end needle valve to max lean rpm and then richen the high end needle mixture by 400 rpm or so when you pinch the fuel line briefly at full throttle the engine speeds up a little and then returns to its setting. The pinch test verifies if you are too rich or too lean. If you are too lean, when you pinch and release the fuel tubing the engine will die or not speed up at all. If you pinch and release and engine speeds up a lot, you are too rich, etc..etc.. The right setting is when your engine speeds up a little, about 300-400 rpm (a tach would help with getting your ears tuned in this area)
have fun and just use a methodical method to tune your needles. Remember, high end needle normally works at 1/2 throttle and above and low end needle affects the idle and transition to full throttle. Also, if you adjust low end, you must check and adjust high end. The two needles can interact with each other. If you forget which direction to turn the needle, just use a clean piece of fuel tubing attached to the carb and blow into it to determine if your adjustment reduced the flow or increased the flow for whatever needle you were adjusting. Its really simple once you get the hang of it and this procedure will make you the club engine expert tuner!
Try resetting your low end needle. Open carb to about 1/4 throttle setting. Turn high end needle about 5 turns from closed. Open carb to full throttle and use a clean piece of fuel tubing attached to the carb and blow into it with your mouth. This ensures your high end needle is allowing fuel (in this case air) to flow into the carb. If it doesn't, than try another turn out or finding the obstruction.
Once you've verified the high end needle valve is working properly and allows air to be blown into the carb at full throttle, now (keep the same high end needle setting 5-6 turns out) and close throttle to about 1/4 throttle setting. Turn low end needle valve so it is completely seated (meaning closed byturning it clockwise, do this gently and don't force anything). Now with the carb opened at 1/4 throttle setting, SLOWLY rotate the low end needle valve counterclockwise (to richen the low end mixture) while simultaneously trying to blow air into the carb through the clean fuel tubing. Stop richening the low end needle valve when you first "feel" (more accurate) or hear air leaking into the carb.
Now, return to high end needle valve and close it completely and open it about 2 1/2 turns from closed. Recheck to make sure this 2 1/2 turn setting allows air to flow into carb and double check the low end needle setting to see if you can blow air into it with carb at 1/4 throttle setting. If all checks out, then attached fuel tank line to engine, prime engine manually with engine at full throttle, return to slightly less than 1/4 throttle, attached glow driver and start with starter.
As soon as it fires up, don't touch anything. Leave glow driver on and let engine warm up for about 30 seconds. Now with glow driver still on, slowly advance throttle setting. You should be able to get it to full throttle. If it dies from going from 1/4 to 1/2 throttle and above (with glow attached) it probably means you are too lean on the low end needle valve. Just open it (low end needle valve) up a little bit (about an 1/8 of a turn or less). Repeat as necessary until engine can advance above 1/2 throttle without dying. Once it can run at 1/2 and above, remove glow driver and go to full throttle. At full throttle, lean out high end needle valve to max lean rpm and then richen the high end needle mixture by 400 rpm or so when you pinch the fuel line briefly at full throttle the engine speeds up a little and then returns to its setting. The pinch test verifies if you are too rich or too lean. If you are too lean, when you pinch and release the fuel tubing the engine will die or not speed up at all. If you pinch and release and engine speeds up a lot, you are too rich, etc..etc.. The right setting is when your engine speeds up a little, about 300-400 rpm (a tach would help with getting your ears tuned in this area)
have fun and just use a methodical method to tune your needles. Remember, high end needle normally works at 1/2 throttle and above and low end needle affects the idle and transition to full throttle. Also, if you adjust low end, you must check and adjust high end. The two needles can interact with each other. If you forget which direction to turn the needle, just use a clean piece of fuel tubing attached to the carb and blow into it to determine if your adjustment reduced the flow or increased the flow for whatever needle you were adjusting. Its really simple once you get the hang of it and this procedure will make you the club engine expert tuner!
06-28-2003 | 07:40 PM
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From: Minot AFB, ND
Help!! Engine Problems
Well homebrewer, I printed out your instructions and and followed them exactly and it worked! I'm still new at this hobby and my weakest area is engines. Now I have one more problem. When I remove the glow starter the engine quits. What could be the solution to this problem? Thanks for the help guys.
06-28-2003 | 11:25 PM
#7
My Feedback: (8)
Help!! Engine Problems
Bruce,
Your engine being inverted is an important factor which makes your needle settings more critical. An inverted engine is much more likely to die from a too rich mixture quencing the glow plug. Starts on an inverted engine are often more difficult since it is much easier to overprime (flood) an engine and quench the glowing glow plug.
Right now replace that Non-OS plug and put an OS 8 or OS 3. Both are pretty hot plugs and work great.
If rpm drops a great deal when a glow driver is removed it can mean that the plug is too cold or the mixture is too rich. If your engine dies when glow driver is removed, it probably means your mixture is too rich.
So, get your engine running again at whatever throttle setting works. If you get it running at 1/4 throttle that is fine. With engine running at 1/4 throttle pinch fuel line and hold until engine dies. If engine speeds up a bunch and takes longer than 2.5 seconds to die than than the needle valve (low end in this case) is too rich. Make very small adjustments. You may have to start and stop the engine 4-10 times to get it dialed in right. Patience is extremely important. With each attempt at same throttle setting, 1/4 throttle in your case, remove the glow plug. If it keeps dying and pinch test verifies that it si too rich by taking longer than 2.5 seconds to die with pinch and held then adjust again. Once you can get it to run without a glow driver you are now much closer to getting that puppy out to the field.
Ok, we now assume you got the engine to idle at 1/4 throttle without a glow driver attached. Now slowly transition to full throttle. Have someone hold or tie the airplane down during this step. With transmitter in one hand, as you advance throttle keep listening to what your engine is telling you. If the engine stumbles and spits out a lot of fuel but is still running then you are too rich on high end (when above 1/2 throttle this needle valve is the one that is adjusted). To verify mixture is too rich, as your are transitioning, don't be afraid to pinch and release the fuel tubing. In some cases you can keep an engine that is too rich from dying by manually controlling (leaning) the fuel mixture with repetitive pinching/releasing until you can get to the high end mixture needle and close her about an 1/8 turn at a time.
Eventually you will get to full throttle from your start idle 1/4 throttle setting. Once at full throttle let her warm up for about 15 seconds before you do anything. After 15 seconds or so, pinch fuel tubing and release (hold until engine just appears to be dropping off from fuel starvation, about 1/2 second). If engine speeds up too much, lean out a little bit at a time. If engine doesn't speed up at all, richen a little. Once high end needle is set, return to your 1/4 throttle setting and check your transition from low to high. If the transition is a little rouch and stumbles but doesn't die, don't worry. Your engine is still new and you should focus on setting the idle and transition only after you've got at least 45 minutes of run time on the engine.
To break in the engine, run at full throttle about 400-500 rpm shy of max lean rpm (if your engine runs without glow and it speeds up a bunch when pinches, this is fine) A little richer than normal is ideal for breakin. The process I gave you above for setting your needle setting is more for flying after engine has been broken in. You should run her slightly rich but not so rich that she is 4 stroking and needs glow power. Run engine for 2 minutes 1st time at full throttle. Let cool completely, start and run for 4 minutes next time (each time ensuring with pinch test you are not too lean or too rich). Repeat after each cooldown doubling the time run. After 30-45 minutes you can now focus on the low end mixture. This is an art and has a lot to do with listening to what your engine is telling you.
The best way to fine tune your low end is as follows. Start engine, run to full throttle, let warmup and set high end needle 400 rpm shy of max lean (verify with pinch test). After engine is warmed up, go to idle and snap throttle to full throttle. If engine stumbles and burps and spits out fuel, the low end is too rich. Make very small adjustments. Low end is set when engine snaps to full throttle and can run about 1 minute at idle without loading up. Loading up occurs when a too rich low end needle valve mixture allows too much fuel to pool up in the crankcrase. At idle an engine may not have enough vacumn to suck all of that fuel. When you transition to full throttle it gets sucked in by the engine vacumn and causes your engine to stumble, smoke, and occasionaly quency the glow plug. If low end is inadvertently set too lean, engine will just outright quit at idle or when you snap the throttle to full throttle. Its that simple. It just takes patience and SMALL adjustments.
After you have set your low end, double check your high end. The low end can affect the high end setting but usually not vice versa. Once the low end is set the only setting you will ever have to touch is the high end (unless you switch fuels or move to a higher altitude).
Good luck and please let me know how it goes.
Glood luck,
Andy
Your engine being inverted is an important factor which makes your needle settings more critical. An inverted engine is much more likely to die from a too rich mixture quencing the glow plug. Starts on an inverted engine are often more difficult since it is much easier to overprime (flood) an engine and quench the glowing glow plug.
Right now replace that Non-OS plug and put an OS 8 or OS 3. Both are pretty hot plugs and work great.
If rpm drops a great deal when a glow driver is removed it can mean that the plug is too cold or the mixture is too rich. If your engine dies when glow driver is removed, it probably means your mixture is too rich.
So, get your engine running again at whatever throttle setting works. If you get it running at 1/4 throttle that is fine. With engine running at 1/4 throttle pinch fuel line and hold until engine dies. If engine speeds up a bunch and takes longer than 2.5 seconds to die than than the needle valve (low end in this case) is too rich. Make very small adjustments. You may have to start and stop the engine 4-10 times to get it dialed in right. Patience is extremely important. With each attempt at same throttle setting, 1/4 throttle in your case, remove the glow plug. If it keeps dying and pinch test verifies that it si too rich by taking longer than 2.5 seconds to die with pinch and held then adjust again. Once you can get it to run without a glow driver you are now much closer to getting that puppy out to the field.
Ok, we now assume you got the engine to idle at 1/4 throttle without a glow driver attached. Now slowly transition to full throttle. Have someone hold or tie the airplane down during this step. With transmitter in one hand, as you advance throttle keep listening to what your engine is telling you. If the engine stumbles and spits out a lot of fuel but is still running then you are too rich on high end (when above 1/2 throttle this needle valve is the one that is adjusted). To verify mixture is too rich, as your are transitioning, don't be afraid to pinch and release the fuel tubing. In some cases you can keep an engine that is too rich from dying by manually controlling (leaning) the fuel mixture with repetitive pinching/releasing until you can get to the high end mixture needle and close her about an 1/8 turn at a time.
Eventually you will get to full throttle from your start idle 1/4 throttle setting. Once at full throttle let her warm up for about 15 seconds before you do anything. After 15 seconds or so, pinch fuel tubing and release (hold until engine just appears to be dropping off from fuel starvation, about 1/2 second). If engine speeds up too much, lean out a little bit at a time. If engine doesn't speed up at all, richen a little. Once high end needle is set, return to your 1/4 throttle setting and check your transition from low to high. If the transition is a little rouch and stumbles but doesn't die, don't worry. Your engine is still new and you should focus on setting the idle and transition only after you've got at least 45 minutes of run time on the engine.
To break in the engine, run at full throttle about 400-500 rpm shy of max lean rpm (if your engine runs without glow and it speeds up a bunch when pinches, this is fine) A little richer than normal is ideal for breakin. The process I gave you above for setting your needle setting is more for flying after engine has been broken in. You should run her slightly rich but not so rich that she is 4 stroking and needs glow power. Run engine for 2 minutes 1st time at full throttle. Let cool completely, start and run for 4 minutes next time (each time ensuring with pinch test you are not too lean or too rich). Repeat after each cooldown doubling the time run. After 30-45 minutes you can now focus on the low end mixture. This is an art and has a lot to do with listening to what your engine is telling you.
The best way to fine tune your low end is as follows. Start engine, run to full throttle, let warmup and set high end needle 400 rpm shy of max lean (verify with pinch test). After engine is warmed up, go to idle and snap throttle to full throttle. If engine stumbles and burps and spits out fuel, the low end is too rich. Make very small adjustments. Low end is set when engine snaps to full throttle and can run about 1 minute at idle without loading up. Loading up occurs when a too rich low end needle valve mixture allows too much fuel to pool up in the crankcrase. At idle an engine may not have enough vacumn to suck all of that fuel. When you transition to full throttle it gets sucked in by the engine vacumn and causes your engine to stumble, smoke, and occasionaly quency the glow plug. If low end is inadvertently set too lean, engine will just outright quit at idle or when you snap the throttle to full throttle. Its that simple. It just takes patience and SMALL adjustments.
After you have set your low end, double check your high end. The low end can affect the high end setting but usually not vice versa. Once the low end is set the only setting you will ever have to touch is the high end (unless you switch fuels or move to a higher altitude).
Good luck and please let me know how it goes.
Glood luck,
Andy
06-29-2003 | 11:11 PM
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From: Minot AFB, ND
Help!! Engine Problems
Well I took her up for her maiden flight and she performed flawless! I finally tuned the engine in just right and she ran like a dream. I really appreciate all of your help Andy. If it wasn't for your advice I would still be adjusting the engine. Thanks again for all of your help.
