Tuning help... I'm Lost

Old 05-11-2012, 05:42 PM
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Exclamation Tuning help... I'm Lost

I have a Losi 454 and have been trouble tuning it correctly for the last few days. Last week it was running perfect, all of a sudden it started flaming out. It kept flaming out and as I leaned the engine, the problem slowly diminished, I was then at a point where my engine was running at 220 degrees Fahrenheit but was so lean on the bottom that when doing the pinch test, it shuts off right away. I was also still having flaming out problems, I tried switching to a cold plug but not difference. My high speed needle was fine, just the low speed. Also, the engine would increase RPM while on the starter box without the carb slide moving! I can't get the engine to stay on now, without leaning it soo much, even though my temps dont raise over 230 farenheit! At this point, the LSN is 1-1/2 turns out, still flaming out. I also noticed the performance of the car, in between flame-outs, is less than it was before. The idle is very inconsistent, and from what I heard, when the idle is inconsistent, the engine should be leaned more! The idle would raise with no throttle being applied and at times would just flame out on the box.

Help please!! I consider myself a good tuner, but I have no idea whats going on here. Also all the adjustments I am making are to the LSN.

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Old 05-11-2012, 07:25 PM
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maybe too small of idle gap....try enlarging the idle gap and richen the lsn
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Old 05-11-2012, 07:26 PM
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The gap is at about 1mm, but i will try.
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Old 05-11-2012, 07:33 PM
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Originally Posted by chopper82p View Post
I have a Losi 454 and have been trouble tuning it correctly for the last few days. Last week it was running perfect, all of a sudden it started flaming out. It kept flaming out and as I leaned the engine, the problem slowly diminished, I was then at a point where my engine was running at 220 degrees Fahrenheit but was so lean on the bottom that when doing the pinch test, it shuts off right away. I was also still having flaming out problems, I tried switching to a cold plug but not difference. My high speed needle was fine, just the low speed. Also, the engine would increase RPM while on the starter box without the carb slide moving! I can't get the engine to stay on now, without leaning it soo much, even though my temps dont raise over 230 farenheit! At this point, the LSN is 1-1/2 turns out, still flaming out. I also noticed the performance of the car, in between flame-outs, is less than it was before. The idle is very inconsistent, and from what I heard, when the idle is inconsistent, the engine should be leaned more! The idle would raise with no throttle being applied and at times would just flame out on the box.

Help please!! I consider myself a good tuner, but I have no idea whats going on here. Also all the adjustments I am making are to the LSN.

Is the engine broken in or is it a new engine? How much fuel has been run through it? Did you read the Engine Tuning Bible Section?

http://www.rctech.net/forum/offroad-...-bible-22.html

You could view this video. A bit simplistic, but it may help.

http://www.youtube.com/watch?v=4Nt5tA3vRl0
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Old 05-11-2012, 07:34 PM
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Possibly an air leak or too much rod slop. I would lean toward an air leak since it come on suddenly, unless you had a runaway and possibly stretched the rod. If it runs good when its still cool and gets worse as it heats up,then the sleeve is probably worn out.
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Old 05-11-2012, 07:50 PM
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Originally Posted by nitroexpress View Post
Is the engine broken in or is it a new engine? How much fuel has been run through it? Did you read the Engine Tuning Bible Section?

http://www.rctech.net/forum/offroad-...-bible-22.html

You could view this video. A bit simplistic, but it may help.

http://www.youtube.com/watch?v=4Nt5tA3vRl0
About 4 gallons throught the engine and broken in properly, I consider my self a good tuner, I've tuned a few nitro engines to perfection, but i'm lost with this. Must be an air leak or something.
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Old 05-11-2012, 07:51 PM
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Originally Posted by Dirtdobber View Post
Possibly an air leak or too much rod slop. I would lean toward an air leak since it come on suddenly, unless you had a runaway and possibly stretched the rod. If it runs good when its still cool and gets worse as it heats up,then the sleeve is probably worn out.
No runaways, It runs better as it gets hotter but keeps flaming out.
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Old 05-11-2012, 07:56 PM
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And I don't think its an air leak because the engine is running at a below average temperature, not going above 230 while the LSN is only 1 1/2 turns out. If I richen the engine any more than that, its way too rich to stay on and drive.
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Old 05-11-2012, 08:03 PM
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Well 1mm is way to big....drop it ruffly .5... check fuel lines..exhaust gaskets...fresh fuel...a hotter glow plug....make sure u have the copper gasket on the glow plug....air leaks front bearing on engine etc etc etc
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Old 05-11-2012, 08:11 PM
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If it has been running good for 4 gallons and now will not tune out, it's probably not a carb adjustment issue. Something is worn out. I would start by pulling the engine apart and checking the piston/sleeve fit and rod. Assuming you have eliminated easily changeable stuff like fuel and plugs.
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Old 05-11-2012, 08:18 PM
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Ok,I'll try that, my fuel line and exhaust gaskets are fine, im using fresh fuel, and i have the copper glow plug gasket. I'm using a cold plug, I was using a medium plug, but was having the same problems but there is no difference when switching plugs. I cant richen the LSN to the point where the engine passes the pinch test because it would be too rich to run. However the way I have it is at 1 1/2 turns out on the LSN, the pinch test tells me the engine is way too lean, the temps tell me its too rich, and it runs like the LSN is tuned just right, but has an inconsistent idle, keeps flaming out, and does not perform as well as it was 4 days ago.
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Old 05-11-2012, 08:21 PM
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Originally Posted by Dirtdobber View Post
If it has been running good for 4 gallons and now will not tune out, it's probably not a carb adjustment issue. Something is worn out. I would start by pulling the engine apart and checking the piston/sleeve fit and rod. Assuming you have eliminated easily changeable stuff like fuel and plugs.
I don't know, this happened suddenly, specifically the first day it rained, I started it up after the rain stopped and instant flame outs and all down hill from there. Only four gallons, I don't know why something would wear out that quick. Never ran above 260 degrees in its whole life, broken in properly and not beat on.
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Old 05-11-2012, 08:34 PM
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Something could have gotten into the engine during a glow plug change or through the filter. Circlip could have popped out and scarred the piston/sleeve. In my experience, a sudden change in tuning usually means something suddenly went bad. The trick is finding it. Have you tried a different exhaust pipe?
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Old 05-11-2012, 08:37 PM
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I haven't tried a different exhaust, no. I hope nothing is bad with the engine, its only 4 gallons old! But i guess I will take it apart and see whats going on.
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Old 05-11-2012, 08:40 PM
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Went back and reread your first post, sounds like your piston/sleeve is just worn out. If your can, pull both out and see if you can push the piston through the sleeve. It should only go about 3/4 of the way before it sticks. Make sure the piston is at TDC before you remove the back plate.
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