Tuning help
#1
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Tuning help
Need help in regards to a trophy truggy. Having trouble with the motor stalling at around half throttle. Have returned all the needles to factory settings and have slowly been leaning out the high speed but the problem is still present. What am I not doing, what should I be checking?
Thanks in advance.
Thanks in advance.
#4
I the o-rings have shrunk, the needles will screw themselves in or out - rarely if ever do they leak air. Try driving the truck around with the glow driver attached. If the engine doesn't quit with the driver attached, the needles are still too rich. Also keep in mind - the idle needle controls fuel mixture up to about 60-70% throttle travel and while the main needle controls fuel mixture above that, it controls overall fuel flow too. If the main needle is too lean, it will interfere with the idle needle. Generally you set the main needle (high speed) first and set the idle mixture second, but only when the idle needle is "in the ballpark". If the idle is way too rich, often you will get too lean on the high side. It would also be a good idea to ensure the idle gap isn't too large. Many manuals spec a 1mm gap and 99% of the time that's way too big. .5-.6mm is a good starting point. Make sure the throttle linkage doesn't bind at all and the throttle closes against the throttle stop easily and quickly when the trigger is released to the neutral position.
#8
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could have a bad piston and sleeve, i bought a savage 5.9 one time that idled fine and was good for about 60 percent throttle travel but thats what it ended up bein. does is run better when its cold or once it warms up?
#10
Clean the air filter?
Worn out piston/liner sets will start and run when cold, but as soon as the engine warms up enough, the engine will overheat and quit and not restart until it's cooler back off. An engine that runs rich no matter where the needles are set usually indicates an air restriction causing the engine to draw more fuel.
Worn out piston/liner sets will start and run when cold, but as soon as the engine warms up enough, the engine will overheat and quit and not restart until it's cooler back off. An engine that runs rich no matter where the needles are set usually indicates an air restriction causing the engine to draw more fuel.
#14
Sounds like the idle needle is still too rich. Post links from YouTube in your thread. Uploading to YouTube works best usually.
#17
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Here's vid 1 of two:
https://youtu.be/yFg3gCO60Z0
Here's vid 2:
https://youtu.be/Wjdpjl7OybA
Temps when idling away were up around 92deg Celsius. Hopefully you can see the amount of oil coming out the exhaust. I also had the filter off and quite a lot of fuel was splashing out from the carby.
https://youtu.be/yFg3gCO60Z0
Here's vid 2:
https://youtu.be/Wjdpjl7OybA
Temps when idling away were up around 92deg Celsius. Hopefully you can see the amount of oil coming out the exhaust. I also had the filter off and quite a lot of fuel was splashing out from the carby.
#19
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Yeah I did but it still stalled. Which needle would be the first to lean out? Would it be possible that one of the needles is letting too much fuel through even after moving the needle settings?
Last edited by shannon23455; 06-30-2016 at 08:08 AM. Reason: Added words
#20
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id there is fuel actually splashing outta the carb, i think something is wrong with your high speed needle. a oil dripping from the pipe is normal, since the fuel does have oil in it, just a byproduct of a nitro engine.screw the high speed needle all the way out and inspect it and its bore. some way or another its gettin too much fuel.
#21
What at fuel and glow plugs are you using?
FWIW - if the settings are too rich, it's not uncommon to have raw fuel coming out of the exhaust at idle. It's common to see the carburetor spit fuel too in overly rich conditions, but it's usually not noticed since ground based engines really shouldn't be run without an air filter for any length of time. Airplane engines will spit fuel at WOT when set to a "perfect setting" and it's visible with a good camera. It happens due to a phenomenon called fuel stand-off or carburetor stand-off.
Last edited by 1QwkSport2.5r; 06-30-2016 at 09:04 AM.
#24
I don't think it is because they're not something that usually wears out. If the engine is really old, the o-rings can shrink over time, but if they don't unscrew themselves, the o-rings are fine. Contrary to what some guys say, bad o-rings will not cause an air leak except if the o-ring under the carburetor is bad or missing.
I think 90% of your problem lies with the needle settings.
What at fuel and glow plugs are you using?
I think 90% of your problem lies with the needle settings.
What at fuel and glow plugs are you using?